Lydia and her new partner hunt a cleaning lady's killer. John and Ben rescue an officer during a bank-robbery shootout. Nate and Sammy investigate the murder of a gang member.

Sammy and Nate feel threatened when Sal calls in Lydia and Josie to help them solve a series of gang murders.

Ben seeks revenge when his mother's rapist is released.

Sammy & Nate get into a deadly gang confrontation. Ben makes a series of rookie mistakes and Lydia works a gang homicide that leads to an unorthodox killer.

Lydia and Josie catch a complicated rape case on the Westside. John bonds with an abandoned teenager, while also having to deal with testifying at his own father's parole hearing.

While working a celebrity murder, Lydia discovers the pros and cons of being in the spotlight.

Lydia gets suspended from duty and bonds with an injured witness. A high-speed chase haunts Chickie, and John tries to clean up a neighborhood.

Sammy seeks answers in the desert. Lydia and Josie babysit an important alcoholic witness before a murder trial. And John and Ben go against procedure to help a child in need.

Ben deals with John's escalating drug problem as Sammy prepares for fatherhood. Lydia embraces a teenage victim and fights her emotions during a high-octane shootout.

On Ben Sherman's final day as a rookie, challenges abound -- none more daunting than how to handle his partner's growing reliance on painkillers.