Three years after being shot, falling out of a window, dying, and coming back to live, David Creegan is assigned to work with Detective Susan Branca. Their first case is disappearance of three boys.

The team hone in on a suspect who is linked to a string of similar killings. However getting hold of enough evidence to tie him to the crimes remains elusive. Meanwhile, time is running out for the kidnapped boys.

A woman is burned to death with strange markings on her body, which draws similarities to a previous victim. Creegan and Branca investigate, and think their perpetrator is man obsessed with fire.

Three women are found beaten to death outside of a strip club. All three were dressed like Justine Hazelton, a former prostitute serving time for murdering six pimps in the early 1990s.

The team are searching for a serial killer, nicknamed the Hangman. Stephen Laney, a reporter and a former acquaintance of Branca's, has been following the Hangman's murder spree for a year.

The bodies of three men are found at a monument. They all have the same heart tattoo and drilled holes in their heads.

Four teenagers mutilate horses and film their antics, but one of them backs out. The OSC intervenes as they think that whomever attacked the horses will eventually kill people.

A girl named Emily Akins is murdered, and the suspect is Mr. Clean, a serial killer who is out on parole but is missing.

A couple is found shot in their own home and their son is missing. Their murder is connected to a string of murders done by a man nicknamed the Morning Person.

Creegan's friend Cyril is arrested on suspicion of being involved in a spate of fatal knife attacks on smartly dressed men, but a lack of evidence hampers the investigation - until an eyewitness account places him at the scene of one stabbing.

A man finds his wife's dead body in the trunk of his car, with her heart removed. Branca, Rivers and Enright travel to Port Endicott, Oregon where there have been similar cases.

The San Francisco team investigates the mysterious deaths of patients in intensive care, who were being treated by a doctor known to be sympathetic to mercy killing.