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.

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.

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. Meanwhile, Chen befriends a reporter whose motives are not clear.

When a new designer drug hits LA streets, it turns users into “zombies,” and Officer Nolan and the team have a Halloween they won’t soon forget. Back at home, Lucy questions whether her apartment building might be haunted.

Desperate to break free from his connection to Elijah, Wesley tries to plant a listening device in his office to incriminate him; Officer Bradford and his sister, Genny, learn an unsettling truth about their father.