The team goes on a city-wide hunt for an individual who is threatening a mass casualty event. Meanwhile, Tim’s sister Genny shows up unannounced with some surprising news, and Lopez continues her inner struggle over Wesley’s deal with Elijah and tries to come up with a plan to get them out of it.

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.

Officer John Nolan is moving closer to his new role as a training officer. In preparation, he is tasked with overseeing Officer Aaron Thorson and must uncover the truth about another officer’s suicide. Meanwhile, Lucy’s successful undercover assignment earns her an invitation for specialized training in Sacramento and she must decide if this is the path she wants to take.

Officer John Nolan and the team investigate the unexpected death of a suspect in police custody. Their search also uncovers a very delicate loose end that could jeopardize Officer Celina Juarez's career. Meanwhile, Sergeant Grey and his wife, Luna, go to New York to visit their daughter, Dominique, only to realize she never made it home from the night before.

The search for a missing boy leads the team into the middle of a dangerous drug war between two rival gangs.