Jo Callaghan’s first novel was easily one of my favorite crime stories of 2024. All of the elements that made me love that book are back in Leave No Trace, the second in this series. These include characters with depth (and backstory), a plot that keeps the pages turning, and the use of a unique sidekick to detective Kat Frank.

AIDE is an AI created detective. Through a hologram, he looks very real. His thoughts, although at times concrete because of a lack of understanding of nuance, are often key to the case. It has been enjoyable to watch the “relationship” between Kat and AIDE evolve. That is just one of the joys of the series.

This time, Kat has asked for a “live” as compared to historical case. The one that she is given is rather grim. A man has been found at the top of a local landmark and he has been gruesomely murdered. The case will lead to fear and warnings to young men.

Readers know that the case will be solved. The enjoyment is in watching how the team accomplishes this.

Kudos to the author. I am already eager for book three.

Many thanks to NetGalley and Random House Publishing Group for this title. All opinions are my own.

A team of detectives with an unusual asset confronts a horrible crime

As the Christmas holidays approach DCS Kat Frank is on the edge of depression. She lost her husband unexpectedly the previous year, her son has left their home to attend university, and she is rattling about the house alone. Her work is her tether to the real world and she pushes her boss to assign her and her relatively newly formed team, the FPU (Future Policing Unit) a real case rather than the the cold cases they have to date been given. Her four member team is unique in that her partner Lock is not a human partner, he is an AIDE (Artificially Intelligent Detecting Entity), and this partnering of an AIDE with a team of detectives is a new experiment. Although initially reluctant to expand the team's remit to working a live case (as he is somewhat hostile to the concept of AIDEs, fearing that they will replace rather than enhance existing police personnel) her boss relents when the dead body of a young man is found naked and gruesomely displayed in an isolated area. With little in the way of forensic evidence and no clear motive (could the killer be the victim's fiancee, or perhaps someone from his professional life?), this will prove to be both a frustrating and a highly visible case for the FPU, especially when another dead body is found similarly displayed. With public perception mixed on whether having an AIDE involved is wise and fears of a serial killer on the loose are putting the area on edge, the pressure is on from all sides for the team to identify a suspect and make an arrest ASAP...but Kat isn't convinced that any of their suspects are actually guilty of the crime despite what Lock's algorithm indicates. Data driven logic clashes with instinct and experience...can they find a way to incorporate both sides in time to prevent another killing?
Leave No Trace is a fantastic thriller, a classic British detective story with a. contemporary twist. As we all come to terms with the growing presence of AI in each of our lives, whether or not we like the concept or understand how it works, here the reader is presented with the ethical questions, practical limitations and amazing possibilities that such a tool could bring to policing. Lock can comb through hundreds of thousands of social media posts in seconds, saving the countless hours of human effort needed to achieve the same results, but the search is ultimately only as good as the instructions given. Kat herself has reason to distrust the efficacy of AI (her husband was initially misdiagnosed by someone using AI as a diagnostic tool, and the delayed diagnosis and treatment may have contributed to the ultimate failure to save his life), but also has Lock to thank for saving her son's life during a previous investigation. Many issues currently faced by law enforcement in the UK and beyond...diversity in the workforce, perceived lack of transparency and inequities in the way situations are handled depending upon the identity of the victim and/or perpetrator to name a few...are woven into the plot One of the team members and the professor who created the AIDE have each had less than positive experiences with law enforcement and bring their own reservations and biases to the job. Interesting and well-developed characters and a gripping mystery combine to form an excellent novel, and with it a fascinating premise. This is the second book in the series, but it can easily read as a standalone. Readers of authors like Jenny O'Brien, Val McDermid and Imran Mahmood should add this book (and its predecessor In the Blink of an Eye) to their list of must-reads, as should fans of well-written crime novels. While the topic of AI is prevalent in the story it did not feel to me to be science fiction, so those who are not usually readers of sci-fi should not dismiss this book on that score. I thoroughly enjoyed reading Leave No Trace, found it difficult to put down, and eagerly await another installment in the Kat and Lock series. Many thanks to NetGalley and Random House Trade Paperbacks for allowing me early access to this smart and intricately plotted tale.

If Jo Callaghan's first novel featuring AIDE Lock and DCI Kat Frank, In the Blink of an Eye, was a stand alone, I would have been happy. The fact that it's a continuing series with the brilliant followup, Leave No Trace, I am ecstatic! The murders that the plot centers on are inventive and dark. AIDE Lock is clearly on a learning curve about how to use its vast resources and also understand the intangible human intuition that drives much of DI Frank's investigative process. This novel shows AI's promise as well as its limits (particularly in the physical world). There are side plots as well, most of which are carryovers from the first novel: Kat's rocky relationship with son Cam, DS Browne's coming to terms with looming single motherhood, and DI Rayan Hassan's ambition.
Callaghan is very good at the subtle drop of a clue that the perceptive reader might catch, even if Kat's team misses it, and who doesn't love the feeling of being slightly ahead of the murder team in solving a case?

Another solid thriller by Jo Callaghan! I was excited to see this book because I wanted more from our favorite Detective/AI duo. I enjoy their relationship, especially as AI Locke attempts to figure out the nuances of his human partner.

The mysterious deaths kept me guessing and while it may not be everyone's cup of tea, I do enjoy a good police procedural. I think this works as a standalone but is much better if you have read In the Blink of an Eye first. I am looking forward to see where the next book takes us!

Thank you to NetGalley and Random House Publishing Group for the advanced copy in exchange for my honest review.

In the first book in this series, In the Blink of an Eye, we were introduced to DCS Kat Frank of the Warwickshire Police. When she returns to work after a long absence, she is essentially coerced into accepting the offer of leading a pilot project for police investigations to incorporate an “AIDE” as a team member. AIDE stands for Artificial Intelligence Detecting Entity.

The AIDE program was created in cooperation with Dr. Sophie Okonedo, who has, from family history, a lot of distrust of police methods, viewing them as being dominated by prejudice and other invalid assumptions. She developed an AIDE she calls Lock, thinking that AIDEs can replace the status quo with objective rationality.

You know how they say conflict is necessary to make good fiction? Well, Jo Callaghan must fervently believe that, because in the first book, Kat and Lock are constantly at odds. Sure, Lock steps on toes with his stats-based approach and complete lack of emotional intelligence, but Kat does want to spend any time helping Lock learn. (By the way, I call Lock “he” because when he occasionally projects himself as a hologram, he tends to use Chadwick Boseman as his avatar.)

The pilot project turned into an active crime investigation and, after the case is wrapped up, Kat and Lock are starting to make a working partnership. That brings us to this followup, Leave No Trace. Thankfully, the conflict dial has been turned down a bit. There isn’t nearly so much hostility from Kat toward Lock and Dr. Okonedo toward all of the police. Instead, Kat has learned to take advantage of Lock’s power in data retrieval and analysis and, while he still takes his shots at Kat’s feelings and hunches, he is beginning to see that they are actually the result of years of experience.

The crimes in this book are pretty over the top. One man, and then another, are found naked and hanging from a cross on top of a hill in the middle of winter, both deal from hypothermia. But how did they get there, and why? A solid police procedural follows. I thought this was better than the first book in the series, though I think both books could stand to be tightened up a bit.

A good addition to the rapidly expanding collection of AI driven stories....some of the murder details were a bit gruesome for me but overall an entertaining story!

Thank you to @RandomHouse and #NetGalley for the digital ARC of #LeaveNoTrace. The opinions expressed here are entirely my own.

I love when the second book in a series is even better than the debut and Leave No Trace is exactly that.

After their success solving a cold case, DCS Kat Frank and her AI partner Lock are ready for a new challenge. When a dead body is discovered at the local recycling center, they are assigned to the "active" investigation. The public nature of case thrusts Lock front & center, creating some problems for the team. And when a second body is discovered, the team knows they're running out of time to find their killer.

The characters feel real and authentic and the cases are interesting. But it's the way the author uses AI into the story, showing the benefits and challenges of the technology in a real life setting. I can't wait to see what's next for this series.

In Book 2 of the Kat & Lock Series, the body of a man is found crucified at the top of a hill in the British Midlands. As Kat, with the assistance of Lock—the world’s first AI detective—begin investigating, a second crucified body is discovered. The police are forced to issue a warning to all local men between the ages of 30 and 40 to avoid drinking in pubs, or if they insist on going to a pub do not leave alone, and definitely do not leave with a stranger. This puts the local men in an uproar, and it is up to Kat & Lock to quickly find the killer before they strike again.

I love these books. I really like Kat - she is very genuine, and I love Lock - everything is so literal with him, and he is absolutely brilliant and frequently tactless. The mystery kept me guessing until almost the end, and it is already set up for the next novel. These don't necessarily have to be read in order, since the author does an excellent job recapping portions of the previous book throughout. If you are a fan of mysteries, then you will love this.

Thanks NerGlalley and Random House Publishing for an ARC of this book in exchange for an honest review. I really liked the first book in the series and I was excited to see a second one. This one was probably even better. It was a really hard book to put down. While I figured out part of the mystery earlier on, I still enjoyed seeing how everything played out. There are some very graphic scenes in here, but also a lot of suspense. I do wonder if some chapters at the end could’ve been shortened or eliminated, but I loved the cliffhanger and I’m looking forward to book number three. This is definitely a book worth checking out when it’s released in January 2025.

Leave No Trace by Jo Callaghan – Book 2 of the series regarding an AI intelligence robot helpng out the police on another case. At first I wasn’t sure about this but as I got more into it, I did like the story and some of the information regarding Lock the AI. At times I feel it got too technical and a little much. Storyhwise this was a good read but as I said some of the information regarding Lock was a little much. I can see this possibly happening in the near future if it is not already being used unbekownste to us. This is a story that you have to read and decide for yourself. I did like the story itself but not sure I want to read another one. I will have to decide.

Much like the first installment, this was a pretty basic procedural with some AI mixed in to give it a little update. I appreciated that the science was more often accurate. I find the characters flat and uninteresting. I won't be reading any more of the series.

Every bit as good as "In the Blink of an Eye" the first book in the Kat & Lock series. This is an excellent character driven, police procedural, with AI assistance and it is well written with engaging characters. A well paced murder mystery that manages to also incorporate several significant social issues including misogyny, artificial intelligence, and gender and racial bias. This is the second book in the series and although it can be read as a stand alone, I highly recommend reading starting with the first book, "In the Blink of an Eye." Highly recommended

Thanks to NetGalley and Random House Trade Paperbacks for an advanced reader copy

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.

I loved the first book in this series, but in this second installment, the writing seemed rushed and the tone was quite strident. I would have liked to see more growth in both DCS Kat Frank and the AI Detective Lock as well as in their work relationship, but instead it felt like heavy-handed messaging about sexism and misogyny took center stage. I prefer issues and messaging to be extremely subtle in the novels I read, even (especially?) when I agree with what the author is saying. I was able to guess the killer fairly early on, as well as the motives, which probably added to my frustration with Kat and Lock. I will definitely be reading book three, and I hope Callaghan can right the ship and repeat the magic of book one going forward, as there's so much potential in these characters she has developed. Thank you to NetGalley and Random House for a digital review copy.

This is book 2 of a series, I think you could read as a standalone. DCS Kat Frank wants to be given a 'live' case, something that would give her team a chance to investigate a suspicious death as soon as it's discovered, and she is given the opportunity when a deceased male is found bound to a cross, naked and missing his ears at the top of a 'hill' in a recycling yard. While her team is investigating the death another male is found deceased in a field also tied to a cross and missing his eyes. The two cases are assigned to Kat's team and there is a large amount of media attention due to the manner in which both bodies were displayed, Kat is under pressure to solve the cases. Her AIDE Lock proves helpful again, able to access and collate data into quickly readable bits of info, helping the team move forward, but they aren't moving forward fast enough according to her boss, and she's being threatened with having to turn it over to a task force to solve. I really enjoyed this one, as much as I did the first, the story just flew by, Lock is at times both funny and frustrating and Kat takes pains to remind people not to call the device a 'him' it's a device, not a human. I would recommend and I look forward to the next. Thanks to #Netgalley and #Simon and Schuster for the ARC.

I really enjoyed this follow-up to Jo Callaghan’s innovative debut novel In the Blink of an Eye. British police detective Kat Frank leads a murder investigation team that includes AIDE Lock, her partner on the case and the world’s first AI detective. One of the appeals of the story for me is the well-developed backstories of several characters: ambitious Rayan, single and pregnant Debbie, Kat herself who’s a recent widow, now also facing an empty nest as her only child goes off to university. These features play into the murder investigation plot and add excitement and reading enjoyment.

Jo Callaghan's Leave No Trace is a quick but unique police procedural that focuses on using AI to help track down a serial killer. AIDE lock is a refreshing addition to s typical police investigation. The relationship between DC Kat Frank and AIDE Lock is fun and endearing, almost like a married couple. The rest of the team fits in wonderfully with DC Kat and AIDE Lock to make the story stand out from other police story. I loved Blink of An Eye, the first book in the series, and Leave No Trace is even better. I could read a hundred stories about DC Kat and AIDE Lock and still not get my fill.
Thanks to NetGalley, and Random House Publishing for the advanced copy of the book. The opinions are my own.

I read IN THE BLINK OF AN EYE by Jo Callaghan and was totally on board with this one. This was a fantastic procedural with tension and emotions running high. Loved the characters and the relationship with the AI brainiac. Some of the race and gender statements took away from the story (imo). Kept it from being a 5 star read for me.
Thank you NetGalley, Jo Callaghan and Simon and Schuster UK for the opportunity to read and review this book.

Leave No Trace is the exciting new book in the Kat and Lock series and it did not disappoint.

Kat and Lock have finally been given the first current case after a man is found brutally murdered at the top of Mount Judd.

Kat along with DI Hassan, DS Browne and Lock's mentor Professor Okenado are racing the clock to make an arrest.

Lock , I just love Lock . He is the new way of policing as he is Artificial Intelligence .

It might sound crazy but his personality is developing and humans puzzle him but he can get answers before you can blink.

Tension mounts with every chapter, bodies are piling up.

My only complaint is now I have to wait for Book 3 in what is fast becoming one of my top series to follow.

Please take time to read the authors notes at the end of the book, it is very enlightening.

Thanks to NetGalley and Random House Publishing Group-Random House/Random House Trade Paperbacks for the privilege or reading and reviewing Leave No Trace.

I ended up DNF this book. It was grusome, and way too woke. I am also not a fan of AI so that didn't help