Who is Claire Gravesend? So wonders PI Lee Crowe when he finds her dead on top of a Rolls Royce in the most dangerous neighborhood in San Francisco. Claire’s mother, Olivia, doesn’t believe the coroner’s ruling that she killed herself and hires Crowe to investigate. But the questions about the Gravesend family pile up fast. First, the autopsy reveals round scars running down Claire’s spine, old marks Olivia won’t explain. Then, Crowe visits Claire’s Boston townhouse and has to fend off an armed intruder. He leaves Boston afraid, but finds his way to Claire’s secret San Francisco pied-à-terre. It’s there that his questions come to a head. Sleeping in an upstairs bedroom, he finds Claire, and as far as he can tell, she’s alive.

It’s late Thursday, and Inspector Ross Carver is at a crime scene: a dead man covered in an unknown substance that’s eating through his skin. Suddenly, six FBI agents burst in and haul Carver outside and into a disinfectant trailer, where he’s shocked unconscious. On Sunday he wakes up in his own bed, his neighbor Mia --- to whom he’s barely spoken --- by his side. He can’t remember the past three days. Mia says police officers brought him home and told her he’d been poisoned. Carver can’t disprove her, but his gut says to keep her close.

Gavin Cain, an SFPD homicide inspector, is in the middle of an exhumation when his phone rings. San Francisco’s mayor is being blackmailed and has ordered Cain back to the city; a helicopter is on its way. The casket, and Cain’s cold-case investigation, must wait. At City Hall, the mayor shows Cain four photographs he’s received: the first, an unforgettable blonde; the second, pills and handcuffs on a nightstand; the third, the woman drinking from a flask; and last, the woman naked, unconscious and shackled to a bed. The accompanying letter is straightforward: worse revelations are on the way unless the mayor takes his own life first.

Caleb Maddox is a San Francisco toxicologist studying the chemical effects of pain. He’s out drinking after a bad breakup when a hauntingly seductive woman sits down at his side. He talks to Emmeline over absinthe, but their encounter is fleeting. She brushes her lips on his ear and disappears. He must find her. As Caleb scours the city, he begins helping the city’s medical examiner with a serial-murder investigation. Soon the search for the killer entwines with Caleb’s hunt for Emmeline, and the closer he gets to each, the more dangerous his world becomes.