John's ex-wife asks a favor before he's sent out to catch a rapist who's impersonating a cop. Meanwhile, Susan learns of Sal's affair while celebrating her promotion; and Lydia and Russell work on a double-homicide case.
The murder of a USC student takes investigators to Compton. Elsewhere, John and Ben attend the funeral of a cop and stop in to visit Dewey at his halfway house. And Lydia decides it's time to confront her mother.
Ben goes on his first solo patrol and must track a missing girl; Sammy and Sal have a hard time working with Gil Puente to catch a former gangbanger; Chickie works on being a better cop; and Lydia and Rene help Brianna out with her baby.
Lydia and her new partner investigate a gruesome triple homicide that highlights their different approaches to the job. Meanwhile, Ben expresses concern over John's use of pain pills; and Sammy's troubles with his wife continue.
The second season opens with the search for a senior citizen kidnapped by a drug addict. Meanwhile, the investigation of a freeway shooting threatens an ongoing undercover operation, and Chickie's new partner shoots at a teen and sets off a riot.