Danger is ever-present as the officers of the Mid-Wilshire precinct grapple with the aftermath of a plotted attack on the city of Los Angeles, leaving Officer 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 Bradford reluctantly accepts help from Officer Chen as he prepares for his sergeant exam, and Officer West pursues an unconventional move after finding himself in need of a new home.

Officer Nolan navigates building tension in his relationship with Jessica and a developing rapport with Grace while working a high-stakes criminal case involving an undercover homeland security agent. Meanwhile, Officer Chen meddles with Officer Bradford’s love life, and Officer Lopez learns some surprising news about Wesley.

Officer Nolan gets off to a rocky start after being introduced to his new training officer, Nyla Harper, who has an unconventional approach to police work after her stint as an undercover detective. Meanwhile, Officer Bradford struggles to think of an appropriate birthday gift for Rachel, and Officer Lopez finds herself navigating a case that triggers a personal memory.

As part of their second phase of training, the rookies are asked to develop their first confidential informants. Officer Nolan soon discovers that no two informants are the same and struggles with his newest task. Meanwhile, 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. Meanwhile, Officer Bradford and Office West are assigned a community policing project helping out the Watts Rams as volunteer coaches at their fall clinic, along with Rams players Eric Weddle and Robert Woods.

Officer Nolan kicks off his birthday by babysitting a crime scene at a law office. Meanwhile, Officer Bradford and Officer West are set to receive special awards, and Sgt. Grey rides patrol with Officer Harper after she requests an early annual evaluation.