In the fifth season premiere, Officer Cooper clashes with his new boot Gary Steele (DEREK RAY), while Lydia Adams tries to balance detective work with motherhood.

After Dave Mendoza is injured in a drive-by, Ben takes it upon himself to solve the case much to Sammy's dismay. Lydia regains her footing as a detective while investigating the murder of a female boxer's husband. Tensions between Cooper and Steele finally come to a head during a traffic stop-gone-sideways.

A breakdown in the LAPD's dispatch system makes a difficult job even harder for the cops all of whom are already grappling with communication issues. Lydia, in a moment of weakness, reaches out to her old flame, Terrell (guest star MICHAEL JACE). John is assigned a new partner, veteran cop Henry Hank Lucero (special guest star ANTHONY RUIVIVAR); Ben and Sammy's partnership is strained just as Ben makes a romantic connection on the job with Brooke Riley (guest star ANNIE MONROE).

Lydia and Ruben track the killer of a man whose body was slow cooked down to the bone. John and Lucero settle into their new friendship during a day filled with strange calls. Ben and Sammy respond to an insane bank robbery call in which the suspects throw cash out into the streets as they make their escape in a getaway car.

John is forced to think about what life will hold for him once he leaves the LAPD. Lydia connects with a man she sent to death row earlier in her career. Much to his chagrin, Sammy becomes a tabloid celebrity for the day after a very public act of heroism. Ben makes a dubious decision to get a drug dealer arrested. And a foot pursuit puts Dewey in danger.

The days events bring all of our cops face to face with some of their greatest fears. The death of a baby shakes Lydia to her core. Sammy is questioned by I.A. about his altercation with Tammi. A difficult day on the job causes Cooper to seek solace in Hicks (guest star GERALD McRANEY) but finds none. Ben becomes more deeply involved with Brooke while continuing to see Elena (guest star CARMEN CORRAL).

John takes drastic measures to try to save Hicks while being confronted with demons from his past. Sammys lie about the tape weighs heavily on his conscience. Lydia and Ruben track down a John Doe. Bens relationship with Elena becomes more serious.

The funeral of a major drug dealer brings gangsters of all sorts out of the woodwork. But even with chaos in the streets, our cops learn that sometimes the greatest threats come from within. Investigating the drug related murder of Sgt. Hills son, Lydia and Ruben discover police corruption in the process and clash over how to handle it. Ben suspects that Sammy did not destroy the tape, and decides to take matters into his own hands with tragic consequences. John sinks further into his loneliness.

Chaos reigns in the City of Angels when Cooper and Lucero are kidnapped and held hostage by a pair of tweakers. All of our cops join the frantic search to find their brothers in blue before it is too late. While Sammy searches for Strokeface (guest star MARCELLO THEDFORD), Ben tries to throw him off the trailwhile simultaneously dealing with an increasingly irrational Brooke.