In the season two premiere, detectives Charlie Crews and Dani Reese are on the hunt for a serial killer when three numbered trunks containing suffocated bodies are found scattered across Los Angeles. With their new boss New York transfer Captain Kevin Tidwell pressuring them to get answers, Crews and Reese race to find a connection between the murders before the killer strikes again. Meanwhile, Ted and Crews attempt to track down the daughter, the lone survivor, of the family Crews was wrongly convicted of killing.

The body of a cancer research scientist is discovered literally frozen solid, baffling Crews and Reese. The crime scene suggests that an animal rights group took revenge on the doctor by switching out his oxygen tank with pure liquid nitrogen. As the detectives delve into the victim's tangled private life, they become increasingly skeptical about the identity of the murderer. Meanwhile, Crews is determined to prove Jack Reese was involved in his incarceration, and Ted asks Crews to act as a reference for a business school interview.