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Kat and Lock #2

Leave No Trace

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From the bestselling author of In the Blink of an Eye comes a gripping thriller that pits algorithms versus experience, logic versus instinct, and one undetectable killer versus two extraordinary detectives.

When the body of a man is found crucified at the top of a hill in the British midlands, AIDE Lock—the world’s first AI Detective—and Detective Kat Frank are thrust into the spotlight as they are given their first live case. When a second body is found the police issue an extraordinary warning to local males aged between 30 and 40 years old:

� Avoid drinking in pubs
� If you must go to a pub, do not leave alone
� And definitely do not leave a pub with a stranger

With the national media and local men in an uproar, Kat and Lock have to combine their instincts and algorithms to catch the killer before they can strike again.

400 pages, Paperback

First published March 28, 2024

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About the author

Jo Callaghan

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Displaying 1 - 30 of 468 reviews
Profile Image for Jayme.
1,439 reviews3,951 followers
August 23, 2024
We were first introduced to Kat and Lock in “In The Blink Of An Eye�-the author’s debut novel-a MUST READ if you enjoy Police Procedurals!
See review: /review/show...

DCS Kat Frank is a widowed single mother who trusts her instincts. So, she has her doubts when she is chosen to lead a pilot program called the “Future Policing Unit”which will pair her with an AIDE called Lock (Artificially Intelligent Detective Entity).

The pair are initially assigned to “COLD CASES� and given a very small team to work with: DI Rayan Hassan, DI Debbie Browne and Lock’s creator, Professor Okonedo.

It (Lock) has been programmed with algorithms that are free from bias or prejudice of any kind-which will hopefully lead to more “evidence based� decision making during the investigation of a crime. It/He has been designed to be free from racism, misogyny, homophobia, transphobia or anything else which could influence the direction a case may take.

And, in minutes he can process data that would keep a “human team� busy for a week.

After successfully closing their first “COLD CASE� in book one, the Future Policing Unit is now tackling their first “LIVE� case- that of a man found crucified at the top of Mt. Judd.

It was fun to be reunited with the team, BUT I had a hard time becoming invested in book two.

The debut novel kept me fascinated with the technology of advanced AI, but I guess the novelty somewhat wore off in this sequel. The book followed the same formula as the last, and also included mixed media peppered throughout such as interview transcripts and social media posts.

It just didn’t feel as fresh and original the second time.

And, for some reason, in the first book, DIS Hassan and Browne were always referred to as such, but in this book they were sometimes referred to by title and sometimes by first name-the inconsistency was distracting.

It is definitely a UNIQUE police procedural which will have you pondering what the future may hold, and worth a read-but the sequel didn’t quite live up to the first in the series.

3.5/stars

A big thank you to a special friend who gifted me this signed copy, which I will always cherish. 🎁
Profile Image for Lit with Leigh.
623 reviews495 followers
January 30, 2024
Thank you Simon & Schuster UK for the ARC. IYKYK my reviews are always honest.

writing: solid | plot: unfocused | ending: tbh I'm glad I'm done | 2.5 rounded down i'm sorry

my opinion

I absolutely LOVED book #1 (banger alert was issued) but this? *whispers* no. Tbh I'll probably sound like and old man shaking his fist at kids skateboarding past his house but that is not my intention, so please forgive me. Also, please do not make any assumptions about my political beliefs—just because you vote a certain way, doesn't mean you have to blindly agree with every sentiment associated with that ideology. Thank you for coming to my Ted Talk.

I hate to say this, but this book was trying way too hard to be woke. I think this type of wokeness will appeal to a certain demographic of people that I will not name, but it certainly wasn't for me. Every woman jumped at the opportunity to make a statement about gender inequality, even when it didn't suit their character or the situation.

Is misogyny real? 100%. Is racism real? 100%. But nearly every social commentary moment in this book was a case of trying to make orange juice out of apples. For instance, does DI Hassan expressing concern over Professor Okonedo participating in her first ever press conference because she's a sitting duck for clickbait hungry journalists warrant this accusation of misogyny: "Oh, I see. You think that only a fully trained male police officer can be trusted to talk to the media? Someone like yourself, perhaps?" Girl wut?? The DCS leading the presser is a woman... and the comms director supervising is also a woman........ ???? What's happening?? And does it make sense for a businesswoman who has connections to organized crime to say something like "you think every successful woman must be crooked." But... you ... are... ???? HALP.

What I loved about book #1 was the agenda-free exploration of the pros and cons of generative AI in law enforcement. But due to all the politicking, AIDE Lock played a small role in this book. Yes, there were funny moments that highlighted how irrationally confusing human behaviour is, but other than the new tech involving post-mortems, I didn't get anything else out of it.

The case itself was pretty predictable, which is fine, if the book delivers in other areas. Unfortunately the mailbox remained empty as no deliveries were made (don't worry, I'll throw tomatoes at myself for that one). No spoilies but while the motivation for the baddie was totally understandable, the extra layer of symbolism was too much for me to handle because I was already so annoyed with all the wokeness.

Anyways. This ends on a cliffhanger and yes I will be tuning in. Hopefully she picks a lane or at least chooses the right moments to get her social justice warrior on. Again, I sound like I wear a red hat if you know what I mean, but the "incidents" in this book made absolutely no damn sense. If she had removed a solid 90% of this, it would've been a much more enjoyable read.

pros and cons

pros: some funny moments, prologue was BANGING... GREAT start, interesting to learn about new tech for PMs

cons: switching between job titles and first names (DI Hassan and Rayan) was super confusing and unnecessary, so woke I was an insomniac reading this, symbolism felt forced, trying to do too many things at once � the deep dive into gen AI is enough I promise you

____

and
Profile Image for Dorie  - Cats&Books :) .
1,134 reviews3,694 followers
January 29, 2025
***HAPPY PUBLICATION DATE - I LOVE BOTH BOOKS IN THIS SERIES***

I really enjoyed “In The Blink of an Eye� and was excited to read the second in the Kat and Locke series!

Kat has been working on cold cases with AideLocke and her team. They’ve solved 3 out of 3 cases and Locke is starting to “learn� how humans think and react!

Kat is ready to take on an ongoing case with her team which includes DI Hassan and DS Browne with consulting from Professor Okenado, the creator of AideLocke.

Her Chief wasn’t quite convinced but then he gets an urgent call �. . . the body of a man is found crucified at the top of Mount Judd, AIDE Lock � the world’s first AI Detective � and DCS Kat Frank are thrust into the spotlight as they are given their first live case.� This time people’s lives are at stake.

This book has absolutely ongoing action and tension - I rarely say this but I really couldn’t put this book down!! Jo Callaghan really knows how to write and the characters are well defined and highly relatable.

I found so many passages that I highlighted but I’ll share one that details the difference between AI and a human while they are racing to discover who is committing these horrific crimes and why? “Lock might be able to view thousands of images in seconds . . . but he simply wasn’t capable of making the lateral connections that a diligent, human police officer could�

The Author’s Notes are a must read - she shares some of the reasons why she is writing this series and her personal connection to the stories.

Both of these books are going to the top of my list this year � I highly recommend these to anyone who is curious about how AI might help in the future. I enjoyed this novel immensely. If you are looking for a different slant on police procedurals - look no further than Ms. Callaghan’s books!

I received an ARC of this novel from the publisher through NetGalley. It was my pleasure to read and review this novel.
Profile Image for Nina (ninjasbooks).
1,406 reviews1,324 followers
April 26, 2024
I’ve been waiting for this a long time, and it was worth the wait. It was engaging and the characters spoke to me. The AI angle was still intriguing, it gives the series an edge. Well done!
Profile Image for Kaceey.
1,413 reviews4,266 followers
August 23, 2024
⚠️Outlier review
This book began with an intriguing premise:

On a desolate hill, a man is found naked, mutilated and crucified. It would appear to be a highly personal killing. He does have a fiancé with a weak alibi.💁🏻‍♀� Could it have been work related? Or some sort of twisted religious killing?

As Detective Kat Frank and her team, (including AI-Detective Lock) begin their investigation, a second murder is reported under similar circumstances. Can the team track down this serial killer before he murders again?

Then…out of the blue the author lobs in a statement that to me was absolutely irrelevant to the flow of the storyline. Hmm…it seemed to quickly morph into a platform for all social issues. So distracting that I completely lost focus of the storyline.😫

AI Lock appeared to take a backseat when the primary focus should have been on him. I loved the concept of AI Lock and so looked forward to see how he would assist in this latest investigation.
Equally disappointing, the supporting detectives on the team who added so much in book one, also didn’t get the spotlight they deserved here. A missed opportunity (IMHO).

I do think it’s important to include relevant social issues as it fits a storyline…but it shouldn’t become the major focus in a fictional novel. Personally, I read to escape.

Other readers absolutely loved this book so make sure to read their reviews.

There appears to be a book three on the horizon. Will I pick it up? Yes! I love the characters and hope the magic of book one comes back!

Thank you to NetGalley and Random House Publishing Group
Profile Image for Patience ~ AnotherOddCreature シ.
132 reviews28 followers
October 4, 2024
5� It was as well written and engrossing as book #1 . The AI, the main and supporting characters, and the storyline were brilliant once again in this second book. I'm keeping my fingers crossed for a third book!

I highly recommend it! Enjoy�
Profile Image for Lisa B.
33 reviews8 followers
February 20, 2025
Well � finished this long winded at times, this was so drawn out I nearly DNF saying that I did enjoy the first half of this book but the last the AI feel lost me , I love Kat & Aide plus her crew� will I continue this series well I am still pondering that.


I listened to the audio version narrated by Rose Ackroyd which after a while grated on my nerves.
I will say that if you want to read this series start with Blink Of The Eye as there is dialogue which happened in the first.

This book starts with Kat & Aide looking into a real crime set in Atherstone Warwickshire a man is found murdered at Mount Judd his ears cut off & naked it up to Kat & her team to find the killer, they are famous for solving cold cases, Aide does everything by algorithm’s will they succeeds more bodies turn up ⬆️!


As I said earlier there was so much descriptive dialogue that I found myself losing interest in what was going on.
Profile Image for Sheyla ✎.
1,971 reviews616 followers
March 2, 2025
Why can't AIDE Lock be real?

Detective Kat Frank and AIDE Lock are back together in Leave No Trace.

After solving a cold case, Detective Kat feels lonely. She recently became a widow, and with her beloved son now away at university, she’s alone in their house so close to the Christmas holiday. She knows work can keep her busy and help manage her blues. Needing something to pull her from her dark thoughts, she finds no better way than immersing herself in a new case. Her boss agrees and assigns her their first live case. Kat and Lock must work hard and fast to find the person who crucified a young man in the British Midlands before someone else becomes the next victim.

The first book in this series was unique, introducing the concept of AI assisting in case-solving. In this installment, we see Lock evolving through human interaction. He’s learning human behaviors and developing his own version of them. Kat, for her part, is beginning to appreciate areas where Lock is indispensable to investigations. For instance, the vast amount of data he can process in mere seconds helps prevent delays in a live case

The author does pose an interesting question: Is an experienced human better than a free-of-bias machine, or are they complementary?

I can't wait to see where Jo Callaghan takes this team next.

Cliffhanger: No

4/5 Fangs

A complimentary copy was provided by Random House Trade Paperbacks via Netgalley in exchange for an honest review.

| | |
Profile Image for Emily May.
2,162 reviews317k followers
April 12, 2024
‘Oh my God,� said Kat [...] How could she have been so blind?

Good question, Kat. How could you?

I was so excited for this book after reading earlier this year. I loved the characters and thought the concept of an AI police detective was both interesting and quite plausible. The dynamic between DCS Kat Frank and AIDE Lock was fantastic.

Unfortunately, this sequel gave off the impression of being rushed and poorly-edited. I saw through the mystery immediately, quickly putting the pieces together and figuring out not only who did it, but also why.

It was then very frustrating-- not to mention, boring --to watch the detectives pursuing red herrings and being clueless. I think I'm of fairly average intelligence, so I do expect trained detectives to get there faster than I do.

I actually felt like there was a lot of incompetence all round here, especially with the male characters. I do like all the strong women leading in this book, but I'm not sure why the men have to be either bad or complete doofuses (doofi?). DI Rayan Hassan is so useless AGAIN that it's hard to believe he got this job. When he isn't salivating over Professor Okonedo like a little puppy, he's stubbornly pushing stupid theories. Which was his role in the previous book also-- to keep repeatedly insisting someone did the crime when everyone else can see it's clear they couldn't have.

McLeish, too, is a total fool. It seems his only job is to sit at a desk and bitch at others.

Even Lock, whom I love, had way too many “Huh, humans make no sense� moments in this book. As I said in my review of , if ChatGPT can understand an idiom, then this sophisticated AI should definitely be able to.

Also, while I think myself and the author are probably politically on a similar page (as far as I can tell), even I found the messages here extremely heavy-handed. I felt a bit like I was being lectured to at times. All men are awful or stupid (or dead). And, despite the fact that this book has a female DCS, a female Professor leading the AI experiment, a female minister commissioning the project, a female local businesswoman, and a nonbinary pathologist, all of them seem convinced that men are out to get them.

Of course, the men in this book are so stupid that offensive things just fall out of their slack mouths, seemingly so that the women can give them a telling off.

I think better editing would have polished some of these themes and, had it not been so heavy-handed, . It's important to write about sexism and misogyny, but I don't think it was done very well here.

Yet, I do have hope for this series as Kat and Lock are such strong characters. I know I won't be able to resist reading the next book. I hope it's better.
Profile Image for Judy.
1,423 reviews92 followers
January 5, 2025
This is the second book in teh Kat and Lock series and the first one was a winner for me, so naturally I picked this one up.

Description:
One detective driven by instinct, the other by logic.
It will take both to find a killer who knows the true meaning of fear . . .

When the body of a man is found crucified at the top of Mount Judd, AIDE Lock � the world’s first AI Detective � and DCS Kat Frank are thrust into the spotlight as they are given their first live case.

But with the discovery of another man’s body � also crucified � it appears that their killer is only just getting started. With the police warning local men to be vigilant, the Future Policing Unit is thrust into a hostile media frenzy as they desperately search for connections between the victims. But time is running out for them to join the dots and prevent another death.

My Thoughts:
There were horrific, gory murders in this book. I have to admit, the crucifixtions turned my stomach, so if you are sensitive you may not want to read this. The AI Detective Lock feels so human I felt like he was a person with feelings. Nevertheless, Kat needs to help prove that AI can assist the department in current investigations, so this is the first one for Kat and Lock to work. The investigation is intense and I couldn't put the book down. It's amazing what AI can do, but we certainly need human views to reach good conclusions. This does show how AI could be an asset in police work. I highly recommend to anyone interested in AI or who enjoys police procedurals.

Thanks to Random House through Netgalley for an advance copy.
Profile Image for Mandy White (mandylovestoread).
2,585 reviews760 followers
February 19, 2024
Last year I loved Jo Callaghan’s Blink of an Eye and have been eagerly awaiting the follow up. And it is finally here� what an incredible police procedural drama once again! i just love Kat and her honesty, her passion for her job and her son. Lock once again had me laughing out loud with his words and confusion about what humans actually mean. Such a clever concept.


So DS Kat Frank and AIDE Lock are back, and this time they have a live murder case. Kat is determined that all their hard work on cold cases will be invaluable on a current case and is set to prove this to everyone. And the case is a doozy .. A man is found crucified on a cross, naked, on the top of a hill�.oh and his ears have been cut off. It is close to Christmas and the snow is heavy and so so cold.

An absolute page turner once again, I could not get enough of this story, really having no idea how it would end. I love that we get an opening for the next book too…cannot wait!!

Thanks so much to Simon and Schuster UK and NetGalley for my advanced copy of this book to read. Published on March 28th.
Profile Image for Valleri.
957 reviews30 followers
September 18, 2024
"I couldn't have solved the case without my team. Or Lock, sir."

I know that some reviewers have written they liked this book less than the first. Not I. I liked Leave No Trace every bit as much as I liked . Are these books 100% logical or realistic? No! I'm not sure why, but I love that about them!

Here is one of my favorite parts:
"So you're my wild card, Lock. I want you to unsettle her by looking clever and all-knowing."
Lock turned towards her, its expression unfathomable in the fading light. "In other words, you want me to be myself?"
Kat laughed. "Was that a joke?"

HUGE thanks to both #RandomHousePublishing and #NetGalley for the opportunity to read and review an early copy of Leave No Trace. This book is #2 in the Kat and Lock series, and has an expected publication date of January 7, 2025.

#JoCallaghan #ScienceFiction #Mystery #Suspense
Profile Image for Jane.
202 reviews62 followers
September 1, 2024
Kat, Lock and her team are back! This time they are working on a live murder case!. Lock is programmed to think logical whereas Kat can also rely on her emotions, can these two join forces again and catch a killer!

!really enjoyed the relationship between Lock and Kat, it felt like they were both closer in this book! The police investigation was really interesting and I did not guess who the killer was, this was a real race against time story which had many twist and turns!I hear book 3 is out next year and I’m looking forward to it!
Profile Image for Shannon M (Canada).
438 reviews144 followers
May 5, 2025
After reading "In the Blink of an Eye" and thoroughly enjoying it, I placed a hold on its sequel LEAVE NO TRACE, which I recently finished. I liked this follow-up as much as the first book, with one exception—a reservation I'll describe at the end of this review.

Synopsis

In the first book in this series, DCS Kat Frank was paired with an artificial intelligence detecting entity (AIDE), actually a monitor that Kat wears around her wrist, but one that projects human-like holographic forms that can talk and be seen. The most commonly used hologram is a black man called Lock. With Lock's help, Kat was able to solve two missing person cold cases.

In LEAVE NO TRACE, Kat and Lock are assigned a current murder case—a man crucified on Mount Judd in the freezing cold and snow, his ears cut off. This is quickly followed by another murder, again a crucified man, this time missing his eyes.

Kat's team consists of Lock, who can analyze internet data at a speed no human could possibly emulate, DI Rayan Hassan who conducts interviews, and 8 months pregnant DS Debbie Browne, who helps manage scenes and sometimes assists with interviews.

The case becomes a feeding frenzy for the media, and Kat struggles with keeping Lock from blurting out inappropriate remarks:

Kat: 'It's called empathy, Lock. Being able to put yourself in the shoes of another human being and imagine how they might feel or react is an essential skill for detectives.'

Lock: '...the multitude of inconsistent and contradictory comments made by humans makes it extremely difficult to understand their objectives, let alone deliver them.'

The climax builds as DI Rayan becomes a possible casualty after he believes he has identified the serial killer.

My Reactions

There was a lot of humour in Lock's difficulties with understanding human's verbal interactions; he (it) is confused by sarcasm and the fact that people often don't say what they mean. Especially comic is the fact that Lock has not developed tact—blurting out information that embarrasses Kat.

Also, the author continued to describe Kat's strong emotional pains stemming from the loss of her husband, a definite plus in the first book, and here, in the second instalment, manifesting itself in the loneliness of trying to cope with an empty house now that her son has left for university.

The humour and Kat's emotional reactions were two strong pluses that were carried over from "In the Blink of an Eye"

In addition, the mystery was top-level, with the killer a definite surprise, even though 'on hand' from early in the story.

What I Didn't Like

There was only one thing I found disturbing in this story, and that was the fact that the killer was presented as a victim rather than as a mentally disturbed person. That the killer had suffered a trauma was undeniable. But the fact that they didn't lash out immediately after the traumatic event occurred, but waited several years to obtain their revenge, meant that they were seriously mentally ill, and should have been presented as such. Instead, they were depicted as 'righteous' by eventually taking vengeance against those who—several years before the story (and killings) began—had committed the crime that caused the killer's trauma. I don't blame the author for this depiction. If you read the 'author's notes' (something I always do), you will find that the author is an expert in Artificial Intelligence, but not in psychology, and she was relying on psychologists to give her insight into how the victim of a traumatic assault might react. Psychologists (and I am one) do not have magical insights into how the mentally ill might react; they rely on statistical analyses, just like Lock. Recent newspaper articles tell us that these statistical analyses can be incorrect, to the detriment of the community at large. In several instances here in Canada—one very recently—mentally ill people have killed innocent people (including children) because the people in change of monitoring the mentally ill have gotten it wrong. Then the killers undergo a 'mental health evaluation', and if found 'not responsible' due to mental illness, undergo treatment for a few years and are released again into the community.

As stated by the parent of a child killed in a horrific incident in a newspaper account of a mentally ill killer in Montreal:

"It's shocking to us to see how they talk about him," said parent.... "It feels like he's the victim." ... "I feel there is no justice at this point. I feel like criminals have more rights, have more care than all the victims," she said.

I am not advocating for jail time for such mentally ill killers, but they should be incarcerated in a mental facility for the rest of their lives. Those in charge of the mentally ill operate on a 'best guess' process according to their own biases. And too often, within the Justice System, they have the discretion to determine whether the mentally ill should be released from custody after committing a heinous crime.

I should add that the author apparently supported the 'killer-as-victim' viewpoint, but then included an ending that evaded the question of appropriate punishment—in other words gave us a 'Justice Prevails' ending, which is why I am moving my 4.5 star rating up to 5 stars.

Thanks to the Greater Victoria Public Library for providing the ebook that I read.

ʴʴʴʴʴʴʴʴʴʴʴʴʴʴʴʴʴʴʴ�
My review for the first book in the series:
In the Blink of an Eye (Kat and Lock, #1)
~~~~~~~~~~~~~~~~~~~~
282 reviews38 followers
May 1, 2024
3.75 / 5

I do have to admit although this book is up there, it’s not as good as the first breakthrough book. I think it’s the agenda pushed behind the book that took alway ounces of the true plots quality but nevertheless a good sequel. I am invested and intrigued to see the direction of the third book! I found the book an easy read, easy to follow plot and easy to grasp. I do think it’s the help from the first book and having that knowledge and understanding there that added to the experience, so I highly recommend those to that start the series to read the first one as this follows the events after.

DCS Kat Frank and AIDE Lock return back, after the reports of a man found crucified at her top of a rubbish mountain (mount Judd), Frank and Lock are tasked to find the killer. A considerable step up from solving historic missing cases. Soon after another body shows up crucified on a farm, pressure is mounting on her to deliver. With personal pressures from her life and work life Kat is put under pressure to be on top of her private and professional life. We gain an insight to the struggles Kat faces and the toll this has on her.

Maybe it’s the way the plot develops or maybe the strategic writing of Callaghan but I was stumped at who the culprit was and surprised at the reveal of the twist. I think my only issue or negative is the hard push on the agenda of the book which dominated a lot of the plot. But I do have to say the amount of politics thrown on this book is alot more than I anticipated. Overall it’s not bad read, worth having a read given that it’s not heavily sci fi focused and still has strong police procedures shown. Excited to see what the next book is installed.
Profile Image for Fictionophile .
1,307 reviews371 followers
January 30, 2025
The first novel in this series, "In The Blink Of An Eye" made my favourite reads of 2024 list. "Leave No Trace" will, no doubt, make my favourites of 2025 list! My first reaction? Brilliant! I loved it, and can't wait to read the next book in the series!

The characters were so well drawn and the police investigation so compelling, that I couldn't turn the pages fast enough!

Detective Chief Superintendent Kat Frank is a forty-five year old widow and the mother of a teenage son. She lost her husband to cancer just a year ago and her grief is still raw. It is coming up to Christmas and her teenage son is away at university, so Kat feels a loneliness she had never anticipated. Her boss puts her on her new team's first LIVE case! Once again, she is to work with an AIDE Lock (Artificially Intelligent Detecting Entity). Her team will include four people if you include the AIDE.

AIDE Lock - is a wristband around Kat's wrist. However, 'he' can be made to look human via hologram. When he is, he is a tall, slim black man. Think Idris Alba with slight touches of Spock.

Detective Inspector Rayan Hassan - is a smart dresser with a law degree and a high conviction rate. He challenges Kat's authority at times and they lock horns on occasion. Rayan is a good friend to his partner DS Debbie Brown. He is smitten with Professor Okonedo, who is in charge of AIDE Lock.

Detective Sergeant Debbie Browne - is a twenty-four year old who has been with the Warwickshire Police for six years. Though a very diligent officer, Debbie has little self-esteem and is constantly apologizing. She is single, and is eight months pregnant. She worries that her condition and imminent life changes will impact on her long sought after career.

Professor Okonedo - a brilliant though diminutive Asian woman with a chip on her shoulder and a huge grievance against the police. She blames them for her brother's unjust incarceration. Though not official a member of the police, she is AIDE Lock's 'handler'.

Up until now Kat and Lock have been working cold cases. Now, Kat and Lock's first live case involves a crucifixion. A young man has been left to die of hypothermia while tied to a crude cross. Just four days after this, another young man suffers the same fate in another isolated location. With intense pressure from the higher ups and the national and international press, Kat and Lock strive to find the perpetrator. Kat's keen sense of justice, her strong moral and ethical compass, and her high-principles, all serve to make her boss, and AIDE Lock, sometime shake their heads.

With themes of gender role, the emotional after-effects of trauma, artificial intelligence, and personal bereavement, this novel was a mesmerizing read. Machine vs. human. How far away from this premise are we really? Not far I think. Machines can make decisions based on facts and algorithms, while humans can make decisions on 'gut instinct'.

The author has taken some elements of her own life and incorporated them into the book - lending the narrative a ring of authenticity.

When reading the pronouns of some of the characters I became a little confused. The pathologist has pronouns of they/them and when reading a sentence, it can be off-putting to those of us who are 'old-school'. I thought it was very amusing when Lock stated his preferred pronouns were he/him. Kat always refers to Lock as 'it', though when he was asked, he said he wants his pronouns to align with his holographic presentation.

I really came to care for all of the characters and I'm eager to learn more about them in the next book. Lock in particular, seems to be becoming more human and the scenes with the horses and the baby were very poignant. I empathized with his plight.

The ending was outstanding and made me SO eager to read the next book "Human Remains". Highly recommended to all fans of well written police procedural fiction.
Profile Image for Erin Clemence.
1,402 reviews397 followers
October 31, 2024
Special thanks to NetGalley and the publisher for a free, electronic ARC of this novel received in exchange for an honest review.

Expected publication date: Jan. 7, 2025

“� is the second novel in the “Kat and Lock� series by . Following a police detective, Kat Frank, and her partner, an AI-generated police investigator named Lock, “Trace� is a detective story for the modern world.

In the middle of a snowstorm, a young man’s body is found naked and crucified on a cross at the top of a local hill. In hopes of raising support and confidence in the police force, Kat Frank and her AI-partner are called in to investigate. It isn’t long after that when a second man is found, crucified as well, and Kat is facing pressure to solve the case before another body turns up. The Future Policing Unit, and Kat herself, are thrust into the media spotlight, which only makes the deadline to solve the crime that much tighter. Kat knows that if she doesn’t get to the bottom of these gruesome murders, her job (and those of her entire team) could be at risk.

“� is the first novel in this series (and, in fact, is the first novel by this author) and I thoroughly devoured it. I loved the idea of an AI-generated detective helping to solve cases, without the emotional components that burden his human counterparts. I was so happy when Callaghan created a sequel, bringing Kat and Lock back into my life!

Although the first novel was fascinating and helped build the backstory of the characters, “Trace� can be read as a stand-alone (but I wouldn’t recommend it).

“Trace� is narrated by Kat, although there are snippets throughout the novel where the serial killer briefly takes over, allowing the readers the ability to see through their eyes, if only for a brief moment. In pure detective drama style, there are plenty of characters with which to choose the suspect from, but the final reveal was as surprising as it was meaningful.

Callaghan’s personal experiences helped create both “Blink� and “Trace� and, although I’m sorry for all of her challenges, I think it has helped to make the stories that much better. I can almost feel the personal connection to both the author and to the novel’s characters. Callaghan’s novel is well-developed, well-formed, creative and engaging and I’m so looking forward to novel number three.
Profile Image for Susie Green.
158 reviews27 followers
January 13, 2024
DCS Kat Frank and AIDE Lock are back with another crime to solve - and it’s their first live case! The body of a man has been found crucified, stripped naked, and with his ears removed on top of a hill. There’s very little evidence to go on, and when a second man is found dead in similar circumstances the police issue a warning to local men that sends shockwaves through the community. The media interest in the case is intense and it becomes a race against time to not only catch the killer but also prove the team’s value.

I absolutely loved this book! It’s current, smart, exciting, highly emotional and it has a really diverse and interesting cast of characters that you’ll feel a genuine connection to. As well as there being a mystery to solve, the book also covers topics such as gender inequality, imposter syndrome, grief, and racism in a way that feels completely authentic to the story. Although this is a crime novel it also feels like an exploration of the human condition, a factor that’s particularly relevant when it comes to Kat and Lock’s relationship.

Kat still has concerns over Lock’s literal interpretation of the English language as well as the impact of technology replacing humans in the workplace - and is she imagining things or is Lock starting to act more human? Just reading these books makes me feel smarter and more knowledgeable about the undeniable impact AI is going to have on all our futures (although I do love it when Lock gets thing’s wrong after luring you in with facts and figures!)

Kat’s home life remains an important part of the story and if anything, things seem to have got even tougher for her. Her son, Cam, has gone to university which leaves her alone in what was until recently a busy family home, amplifying her grief for her husband John. John was the person she turned to at the end of a hard day at work and her partner at couples events they’d previously enjoyed together, but all of that has changed now and Kat has to work out how to navigate this next chapter of her life.

I absolutely loved this book and can’t recommend it enough! The whole book is a masterpiece with the perfect mix of plot and character and I think it’s a series that would be enjoyed by everyone. And no spoilers but the ending will leave your jaw on the floor�
Profile Image for Joanna Park.
610 reviews40 followers
April 19, 2024
Leave No Trace is another gripping, thought provoking book in what is quickly becoming my favourite crime series. It’s going to be a difficult book to review as I really don’t want to give anything away.

Firstly it was great to be back with DCI Kate and her team, especially as I’d grown so fond of them in the first book. The author does a great job of describing the action so that the reader feels like they are actually there as part of the team, watching all the action unfold. I loved following all the characters and discovering more about what had been happening in their lives. All of the team had hidden problems that they were struggling with and it was quite poignant at times to see how much this was affecting them. I especially liked seeing Kat grown in confidence during this book and stand up for herself more.

As with the first book the author sets out a compelling case for the use of AI in police work. I found it fascinating, though a bit frightening, to find out more about what AI could be capable of � especially that it could be capable of human emotions. It was interesting to see it’s limitations too and to understand why it wouldn’t be a good alternative to a real life police officer.

The murder investigation was really interesting and I enjoyed trying to solve it alongside the characters. The investigation throws up some very thought provoking issues which I enjoyed learning more about, especially seeing the different perspectives it throws up which would be very different if it was happening to another group of people. I loved seeing how the investigation unravelled and the reasons for the murders which was different to anything else I’d read before.

Overall, as you can probably tell, I absolutely loved this book and can’t wait to read more in this series. The book is fast paced, with short chapters which make it very easy to read. I quickly found myself hiding away in the kitchen to try and read a little bit more. There were lots of twists to keep me guessing and I liked that I wasn’t able to guess who the murderer was until the end.

Huge thanks to Rhys the rep for Simon and Schuster for sending me a copy of this book. If you’re a fan of crime fiction then you need to read this book.
Profile Image for Tracy Fenton.
1,091 reviews210 followers
April 2, 2024
In the Blink of An Eye went straight into my TOP TEN Books of 2023, so I was absolutely over the moon to read an early copy of book 2, Leave No Trace and jumped at the chance to be part of the epic blogtour organised by Anne Cater of Random Things Tours.

If you haven't read In the Blink of An Eye yet, I would absolutely say READ IT NOW, because Leave No Trace follows on from the first book and whilst you could read it as a standalone, the first book is so superb it would be a shame not to get to know the main characters in greater detail.

So, I will assume you have read the first book and now eagerly await the next book in this cracking, original and clever series, and it's my absolute pleasure to tell you more about Leave No Trace.

This book starts shortly after In the Blink of An Eye ends, set a few weeks prior to Christmas, DCS Kat Frank and AI Lock are tasked with their first "live" murder case. The grisly discovery of a naked man, crucified at the top of a local hill with his ears cut off is the beginning of a very dangerous and gruesome hunt to track down the killer before he or she strikes again.

With huge interest from the media and public, Kat finds herself at the centre of a challenging case facing both public scrutiny and under immense pressure from her boss to solve this crime before the "big guns" from London are brought in.

Once again Jo Callaghan has given the readers such an in-depth and raw glimpse into Kat's life, as a grieving widow and mother to a son who has recently left home for University.

It is however the originality of AIDE Lock, with his plain speaking, factual and observational skills on the human race, that give this series the edge over other police procedurals.

The growing respect and understanding Lock and Kat have for each other is wonderful to read and this series has potential to keep on going for years to come.

I was very honoured when Jo told me that one of the characters, Tracy Taylor, was named after me and delighted to see that finally Jo has spent my name correctly.

An easy 5 stars from me and please, don't forget to follow all the amazing bloggers on the tour - details below.
Profile Image for Monika.
1,153 reviews48 followers
March 22, 2025
Ibland hittar man böcker som verkligen tilltalar en, på många (eller alla) sätt. Det gjorde jag förra våren, när jag läste Jo Callaghans första bok. När andra delen, Lämna inget spår, släpptes i höstas så var jag väldigt sugen på att köpa den, men jag önskade mig den i julklapp i stället. Redan två månader senare så är den läst.

Det som gör de här böckerna så bra, tycker jag, är AI-delen. Det märks att författaren är AI-forskare, för hon får fram både nackdelar och fördelar med AI. Vad är den bra på? Vad är den mindre (inte alls) bra på? Det lyckas hon få med på ett väldigt bra sätt. För egen del så tycker jag det är befriande att läsa något som inte förbehållslöst tycker att AI är lösningen på allt.

Lämna inget spår känns inte lika välskriven som förra boken. Dessutom så tycker jag att boken tappar lite när det är så uppenbart att författaren har en (inte så väl) dold agenda. Nåväl, detta kanske är den berömda "mellanboken". Tredje delen släpps på engelska nu i april. När blir den översatt?

OBS! Detta är en kraftigt förkortad text. Hela finns på
Profile Image for Zoe B .
304 reviews4 followers
January 25, 2024
After devouring In The Blink Of An Eye when I read it late 2022 which was my favourite thriller that year, I couldn’t wait for the next instalment so was super excited when Leave No Trace arrived.

I loved hooking up with DCS Kat Frank and AIDE Lock (the world’s first AI Detective) again this time to catch a killer who is targeting men. With warnings to men to avoid drinking in pubs this caused a national uproar which was interesting how this was examined as it is normally women that have been acknowledged as at risk.

Leave No Trace is so multi layered with the humour that I loved from In The Blink Of An Eye to the emotional aspect of grieving and living a life without a partner which is drawn from Jo’s experiences.
I love the dynamics with Kat and Lock and how the story explores intuition verses Al in the world of policing. Kat has years of experience in police work but Locke has been programmed to read thousands of material in seconds which speed end up certain processes when investigating a case. It also raises the question whether AI can develop feelings and there were a couple of moments where I felt sorry for Locke and forgot that he is not human.

I literally inhaled this book, it really is outstanding and unique and using the cliche ‘I couldn’t put it down� is an understatement and I have no doubt this will be a thriller of 24 for me. Jo is an amazing new talent crafting such addictive thrillers. If you haven’t read In The Blink Of An Eye (which is currently a Sunday Times bestseller) grab a copy which is in supermarkets and 99p on kindle before Leave No Trace is published, you won’t regret it.

PS I’ve got a confession to make; I’m in love with AIDE Lock. I’m thinking Colin Salmon in a TV Series although I think it would be a younger man who plays him

Thank you Likely Suspect and Simon & Schuster for the proof copy
Profile Image for Laura.
417 reviews84 followers
October 4, 2024
Das Team um Kat und den KI Ermittler Lock bekommt nach all den Cold Cases endlich einen aktuellen Fall zugeteilt. Auf einem Schrottplatz wird die Leiche eines jungen Mannes gefunden � gekreuzigt und mit abgetrennten Ohren. Da die Nachricht sofort hohe Wellen in der Presse schlägt, soll dies vor allem genutzt werden, um die Bevölkerung an das Thema KI Ermittlung heranzuführen. Als noch eine zweite Leiche gefunden wird, steht Kats Team unter enormer Beobachtung und hohem Druck, endlich den Täter zu finden. Nicht jeder steht dem technologischen Fortschritt so offen gegenüber�

Nachdem ich mich im ersten Teil der Reihe sofort für die Idee der KI Nutzung begeistern konnte, habe ich mich enorm auf den zweiten Teil der gefreut. Auch Kat hat sich inzwischen regelrecht mit Lock angefreundet und weiß seine Arbeit für das Team zu schätzen. Dennoch gibt es natürlich immer wieder Situationen in denen die zwei aneinandergeraten. Zwar lernt Lock stetig dazu, aber die Feinheiten der Menschlichkeit sind für ihn meist schwer zu fassen. Angefangen vom Bauchgefühl bis hin zu kleinen Alltagslügen. Woher soll eine KI wissen, wann es angebracht ist zu schweigen? Auch die Grenzen der KI werden in diesem Teil näher beleuchtet und auch Locks Umgang damit. Auch der Rest des Teams kommt in diesem Teil nicht zu kurz, so dass wir auch die anderen Ermittler noch etwas besser kennen lernen können.

Der Fall, in dem ermittelt wird, ist dieses Mal gleich zu Beginn sehr spektakulär. Zunächst tappt das Team im Dunkeln, vor allem was die abgetrennten Ohren betrifft. Doch Stück für Stück geht es mit der Ermittlungsarbeit voran, die oftmals durch Lock erheblich verkürzt wird. Aufmerksame Leser, die viel im Genre lesen, könnten vielleicht schon vorzeitig eine leichte Ahnung haben, dennoch war es interessant zu sehen wie das Puzzle immer weiter aufgedeckt wird und verborgene Verbindungen zu Tage treten.

Wieder mal ein sehr gelungener Krimi, der vor allem mit einem sehr spannenden Ende auftrumpfen konnte. Ich habe noch lange nicht genug von Kat und Lock und bin gespannt, wann uns ein neuer Teil erwarten wird.
Profile Image for Dee.
521 reviews11 followers
March 6, 2024
⭐️ 5 ⭐️

In the Blink of an Eye was a phenomenal debut from Jo Callaghan and one of my top reads in 2022, so I can’t tell you how excited I was to get my hands on a copy of Leave No Trace, the second book in the Kat and Lock series.

Leave No Trace can be read as a standalone, but I do think it reads better for knowing more about DCS KatFrank and AIDE Lock (and I can't recommend the first book highly enough).

Jo’s writing is so readable and the story so immersive, I flew through the pages in no time. Kat, Lock, and the supporting cast are all well-rounded, fully fleshed-out characters, and I love the dynamic and witty banter they share. Lock, in particular, is a great character. It is normal to have a bit of a crush on an AI detective in hologram form, isn't it? (asking for a friend, obviously).

Leave No Trace is enjoyable and entertaining; it's a book with an interesting, intriguing, deftly plotted storyline and an ending that left me desperate for more. What’s not to love?

I predict another huge hit for Jo Callaghan, and if the series doesn’t get snapped up and adapted for TV, I’ll eat my hat.

If you’re looking for something new and original to get your teeth into, then look no further.

Can’t wait for book three!

Many thanks to Jo Callaghan and the publisher for my proof copy in exchange for an honest, unbiased review.
Profile Image for Wendy(Wendyreadsbooks) Robey.
1,346 reviews72 followers
March 29, 2024

Fast paced, thrilling, brilliant are just a few of the superlatives I could use for Leave No Trace from Jo Callaghan and all the plaudits received are so well deserved.
I found the AI elements fascinating and scary at the same time - the things Lock could do were so impressive but also slightly worrying. The dynamics between him and Kat were so well written - the balance shown between that need for fact and good old fashioned instinct so clearly needed. Their partnership was so interesting - they both learnt so much from eachother, and their interactions and those of Lock with the other characters formed such an integral part of the story and investigation.

The storyline was more than just about AI though. We had grief, loss, love and trauma, each covered so sensitively and with understanding so that this book with it’s many facets, makes it all the more brilliant.
Profile Image for Karen Kingston.
906 reviews16 followers
January 19, 2024
Loved book 1 and loved this book too. Great to see how Kat’s team has evolved and how Lock continues to help them. Didn’t guess who the murderer was until close to the reveal - this was a tense and addictive read. When will book 3 be published? What a cliffhanger!
Profile Image for Christine.
1,775 reviews39 followers
December 29, 2024
4.5 stars
DSC Kat Frank has been partnered with an AI detective, Lock, as part of a pilot program. In the past, they've only worked on cold cases together, but this time they are working on a current case with a high profile. Not only is Kat's job on the line, but more lives are at risk. I love how well Kat and Lock work together and that at times you can tell that Kat considers Lock even though he isn't human.

The book does a great job of balancing the case, the issues which come up regarding the use of AI, and the personal lives of Kat and the others on her team. Kat and her son are both grieving the loss of Kat's husband so the growth she is showing, and the touching endings are both fantastic and set this book apart from other mystery/thrillers. I loved both this book and the first book in the series (In the Blink of an Eye, which I highly recommend), and I am already looking forward to reading the third book in this series when it comes out.

I received an advance copy of this ebook for review consideration from NetGalley and Random House, but my review is voluntary and unbiased.
Profile Image for itsallaboutbooksandmacarons.
1,939 reviews38 followers
December 8, 2024
Kat Frank and AIDE Lock made a brilliant team, and their investigation was a captivating mix of suspense and discovery. Each twist in the case kept me guessing, with the killer’s identity hidden until the perfect moment. The way the story built up was so clever, and the tension never let up.

The reason behind the crime was devastating, and it added a depth to the story that made it even more gripping. The ending, though heartbreaking, felt inevitable and gave the story a lasting impact. It wasn’t just about solving the mystery—it was about understanding the people behind it all.

The atmosphere of the book was perfectly suited for December. The cold, dark setting created such a sense of unease that made every page feel more intense. I could practically feel the chill of December in the air as the story unfolded. It made the entire experience immersive and unforgettable.
Profile Image for Glo .
100 reviews54 followers
June 15, 2024
This second book was a bit less surprising from the tech point of view, but it's quite entertaining. I like the characters' development and the ideas suggested around the use of AI in real life. I am waiting for the third !)
Profile Image for Debbi Barton.
480 reviews6 followers
November 21, 2024
4.5 🌟 a great police procedural book, following on from her first novel Blink of An Eye. This investigation is around a serial killer on the loose in Nuneaton, using AI to assist. Knocked down by half a star because the client/therapist professional relationship was unbelievable, but didn't detract from a great storyline
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