Austin police detective Sam Cain has struggled for years to balance his job with his family, and he seems to be losing his balance. Haunted by the past--especially an investigation five years earlier into cult murders that ended in tragic violence--as well as the present--a serial rapist Sam helped convict is released from prison due to a clerical error--Sam is thinking about leaving the force. His worst fears are realized when the rapist returns to Austin and claims another victim; a few days later, Sam is stunned when the rapist turns up in the morgue.
More determined than ever to quit, Sam is called into the office of his former supervisor Cap Howser, now an assistant commander. Three murders committed over the past month appear to be related; a known drug dealer and two paroled felons killed execution-style in their own homes; pinned to the clothing of each victim is a slip of paper on which is typed an obscure Biblical name. Howser hands Sam a letter received by the police that morning, an Old Testament rant in which the writer proclaims himself the God of retribution and promises more deaths. Howser wants Sam to take over the investigation. It is the last thing Sam Cain wants; he refuses at first, but eventually Howser persuades him to take the case.
The second last thing Sam wants is a partner. But Joey Gordon turns out to be one surprise after another--young, Latina, and tech-savvy--and before long she has earned Sam's trust. As the body count rises and the killer begins to write letters to the newspaper as well as the police, Sam must not only pursue a faceless killer but also confront his own inner demons. Even as the investigation team grows, Sam understands that the hunt for the killer has become for him intensely personal.
The killer's MO is baffling. There are no signs of forced entry, no signs of struggle; the victims appear to have let the killer into their homes voluntarily. The investigation begins to focus on a handful of suspects: a cab driver who shows an inordinate interest in the murders, is caught lying to the police, and owns a collection of police badges and insignia; a parolee convicted of attempted murder who found religion in prison and moonlights as a fire and brimstone street preacher; and an ex-cop who quit the force after being exonerated of an excessive use of deadly force charge in the death of a suspected drug dealer.
Enlisting the help of a pair of UT linguistics professors, a homeless ex-cop, and unconventional Catholic priest, an FBI profiler, and a self-proclaimed psychic from Seattle, among others, Sam and the investigation team work to slowly tighten the circle around the killer even as the team is torn by dissension. With public pressure mounting, Sam's former departmental nemesis and current head of homicide announces an arrest in the case, over Sam's vigorous objections. When another victim is discovered days later, the suspect is released. As the maelstrom of criticism swirls around the investigation, Sam appears to the be the quiet eye of the storm, for a reason no one could [possibly guess. He believes he has discovered the identity of the killer, and he understands that he may have to do the unthinkable in order to stop the killing.
