This is book 4 of the "Prey" series.

This note contains spoilers for the book.

Lucas Davenport #4.

A rematch with Becker from Eyes of Prey. Mostly it takes place in New York, where Davenport is brought in as a consultant (he's been thrown off the Minneapolis force), and it gets him involved with Lily Rothenburg again; she's chasing rogue cops running a murder ring that only kills intractable criminals.