Leave No Trace - Jo Callaghan *****

By Brian Clegg

In Jo Callaghan’s first book featuring Detective Superintendent Kat Frank paired up with a virtual AI detective called Lock, In the Blink of an Eye, it was arguably the science fiction aspect that came to the fore – but the (arguably better) sequel focuses more on being an excellent police procedural crime novel.

Frank and Lock have been moved from cold cases to a frontline murder that rapidly becomes a national news story – the victim has been crucified. (I don’t know if the release of the book was timed intentionally, but I read it over Easter.) Tension mounts as a second crucified body is found – while the team is still thrashing around trying to find a viable suspect.

Where in the first book, Lock (and people’s reaction to his holographic presence) featured heavily, here he becomes significantly more part of the team, and we see not only his limitations, but some consideration of how much he should be considered a conscious entity. If anything, his abilities are slightly under-utilised. There is also a little less focus on Frank’s home life, which was central to the first novel, allowing the police procedural aspect to come more effectively to the fore. With an impressively structured case to solve, this made for an engaging and intriguing plot.

Leaving aside the technical limitations a real Lock would face – which are fine to make the story work – the only thing I thought was a little odd was that an early potential motive was religion, and at one point we have a suspect saying ‘Christians aren’t the only ones who used to crucify people’. While a religious motive could have been followed up (though it seemed to have dropped early on), in reality Christians would be much less likely to use this method of killing than anyone else.

I suspect some regular readers or viewers of crime stories would have spotted a couple of points ahead of the police team – but that is part of the appeal of reading this kind of book, where the puzzle of working out the who, how and why is just as important as exploring the human interactions along the way. With a dramatic against-the-clock ending, it’s a book any crime lover will relish.

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Now Appearing is the blog of science writer Brian Clegg (www.brianclegg.net), author of Inflight Science, Before the Big Bang and The God Effect.