This is the 12th book in the 'Lincoln Rhyme' series, but can be read as a standalone without missing much.
As the story opens, quadriplegic, forensic criminalist Lincoln Rhyme has given up being a police consultant and is teaching forensics. One of Rhyme's students - thirtyish, wheelchair-bound Juliette Archer - asks to be his intern, and Rhyme agrees.
Meanwhile, Rhyme's professional partner/girlfriend, NYPD Detective Amelia Sachs, is on the trail of a murderer called Unsub 40. Sachs spots Unsub 40 on the street and follows him into a mall, where the perp orders lunch in a coffee shop. Amelia is watching the Unsub and waiting for backup when loud screams erupt from the escalator - which has popped open and swallowed a man named Greg Frommer. When Amelia rushes over to help doomed Frommer - who's practically bisected by the escalator machinery - Unsub 40 disappears.
After learning that Frommer's widow and young son are almost destitute, Amelia convinces Lincoln to help an attorney file a civil suit against the escalator company and anyone else who might be liable. Intern Juliette helps Lincoln research grounds for the lawsuit.
Every book in this series features a clever perp who has some bizarre modus operandi. In this book it's Unsub 40, who's learned to sabotage devices that use 'smart' computer technology, like escalators, elevators, cars, industrial machines, household appliances, etc. (Imagine your electric carving knife suddenly attacking you!)
The Unsub is determined to get revenge against 'Shoppers', and takes credit for each of his kills, calling himself 'The People's Guardian.' Parts of the book are told from Unsub 40's point of view, which provides insight into his thinking and history.
As things play out Lincoln's inquiries for the civil suit dovetail with Amelia's hunt for Unsub 40, and the duo (plus Juliette) collaborate on the forensic analysis of evidence such as dust and debris at crime scenes; glass fragments; wood splinters; furniture glaze; food wrappers and napkins (the Unsub loves White Castle hamburgers); and so on.
There's plenty of excitement as Unsub 40 tries to elude the cops, who are close on his trail. An added element of suspense is the killer's girlfriend, an apparent survivor of domestic abuse, who seems to be in danger from the Unsub.
There are a couple of subplots to add to the excitement. Amelia's former boyfriend, ex-cop Nick Carelli, has been in prison for robbery and assault. Released after five years, Nick claims he was coerced into confessing, and implores Amelia to help him clear his name. And Officer Ron Pulaski - who sustained a serious head injury in the line of duty - is secretly trying to buy a powerful new street drug from gangbangers.
In Deaver's thrillers things are not always as they appear, and I wondered about what was really going on. I also thought there might be a rearrangement of romantic partners: Lincoln and Juliette? Amelia and Nick? Lots to speculate about as I sped through the book.
I enjoyed this fast moving suspense thriller but was a little disappointed with the denoument, which was rather abrupt (....all of a sudden the perp is in custody!). Still, a good addition to the series. Highly recommended to mystery fans.