The officers grapple with the aftermath of a plotted attack on the city of Los Angeles, leaving Bradford fighting for his life.

Nolan teams up with new night detective Nick Armstrong for a murder investigation case that results in an unexpected reunion with a former love interest.

Officer Nolan navigates his relationship with Jessica and a developing rapport with Grace while working a high-stakes criminal case involving an undercover homeland security agent; Officer Chen meddles with Officer Bradford's love life.

Officer Nolan's first day with his new training officer gets off to a rocky start. Officer Bradford struggles to find a birthday gift for a new girlfriend. Officer Lopez has a case that triggers difficult memories.

The rookies are asked to develop their first confidential informants; Officer Chen's mother complicates her home life when she comes to stay with her.

An emergency alert of an impending missile attack sends Los Angeles into chaos and uncertainty, while the officers each try to keep the peace and deal with their own disasters.

John and Jessica's relationship gets a lot more complicated after she delivers some surprising news; Officer Bradford and Officer West are assigned a community policing project helping out the Watts Rams as volunteer coaches.

Nolan spends his birthday guarding a crime scene in a law office. Bradford and West receive special commendation. Harper requests an early annual review.

Officer Nolan's trust is tested. Meanwhile, Officer Harper has finally earned an overnight visit with her daughter that is put into jeopardy when her past undercover life resurfaces again.

Officer Nolan and team are charged with escorting a notorious female serial killer. Meanwhile, Officer Chen meets a seemingly perfect man who sparks her interest, and Officer Lopez worries about Wesley as his PTSD continues to increase.

Officer Nolan and the entire team are in a desperate search to rescue Officer Chen after her abduction and must attempt to get Rosalind to help them in their search.

Nolan takes his son's fiancée, Abigail, on a ride-along after she shows interest in becoming a police officer. Meanwhile, Jackson's relationship is becoming complicated at work.

Nolan is given some life-changing news and invites Grace over for a homecooked meal in his newly remodeled kitchen. Meanwhile, each unit is tasked with following up on dormant cases in the hopes they can uncover new leads.

Officer Nolan is having a particularly bad day after learning his identity has been stolen. Meanwhile, Sgt. Grey must confront his past and testify at the parole hearing of the man who murdered his partner.

Officers Chen and Bradford respond to a call at the Los Angeles auditions of "American Idol" and Officer Chen ends up facing Ryan Seacrest and the judges; Chen befriends a reporter whose motives are not clear

Officer Nolan's relationship with his first confidential informant is tested when he discovers her back on the street dealing drugs.

Officers Nolan and Harper are tasked with escorting four juvenile offenders to a Scared Straight program at a correctional facility that quickly becomes a riotous situation.

In part two of the season finale, Nolan's discovery goes much deeper than he expected and could put his life and career in jeopardy.