John returns to duty after recuperating from back surgery and meets his new partner, Officer Jessica Tang, a tough and disciplined cop with her own set of baggage from working the streets. Lydia, whose new partner is Detective Ruben Robinson, can't seem to escape helping a former CI who seems unable to stay out of danger, Ben, Sammy and Dewey chase an armed man into an elementary school, and Ben bumps heads with an intense street cop whose cynical attitude is affecting their work.

It's Hood Day on the streets of Los Angeles, and Captain Rucker has the department playing hall monitors. Sammy lets old grudges die hard when he leaves a gang territory unattended, only to have a violent gang war erupt throughout the city. Ben's recent mistake continues to haunt him everywhere he goes. Ruben practices his speech for his daughter's Quinceañera in the midst of a murder investigation. Cooper and Tang investigate a robbery in a strict Orthodox Jewish home, leading Tang to reveal parts of her past.