Los Angeles Police Department officers Brian Taylor and Mike Zavala are close friends and partners in the high crime area of South Central in the Newton Division of the LAPD. Taylor, a Marine Corps veteran, records their activities for a college class after they return to duty from a recent officer-involved shooting.

Upon responding to a public disturbance call, Tre, a Bloods gang member, yells racial insults at Zavala, who responds by accepting a one-on-one fist fight. Zavala wins and earns Tre’s respect for not charging him with assault. Later that night, Tre and his fellow Bloods are attacked in a drive-by shooting by the hispanic Curbside Gang. The following night, the officers respond to a noise complaint at a house party where Taylor and Zavala encounter Curbside Gang members “Big Evil” and “LaLa”. Taylor and Zavala rescue children from a house fire while on patrol and are awarded the Medal of Valor.

During a traffic stop, they arrest a man who is in possession of several ornate firearms and large amounts of cash. Taylor urges Zavala to join him in investigating further, leading them to another man guarding a home full of human trafficking victims. When ICE agents intervene, the officers learn that the house is tied to the Sinaloa Cartel and are strongly urged to stay clear due to possible reprisals. Taylor soon becomes engaged to his girlfriend Janet and Zavala’s wife Gabby gives birth to their first child.

One night, Taylor and Zavala respond to a call from their rookie fellow officer, Sook, and find her partner Van Hauser has been stabbed through the eye. They find and rescue Sook, who was being savagely beaten nearby. Taylor marries Janet, and at their wedding Zavala tells Taylor that, should anything happen to him, he will take care of Janet. The next day, the officers perform a wellness check on an elderly woman. In her house, they discover large amounts of heroin, dismembered corpses, and a message from the cartel. Unbeknownst to them, ICE has eavesdropped on a phone call from the cartel in Mexico and hears the two officers have been “green-lit”; Big Evil, LaLa, and others are tasked with killing them.

While on patrol the officers encounter Tre who as a favor from their earlier encounter warns them that some friends who were recently released from Folsom prison learned that both officers were green-lit, but Taylor and Zavala shrug it off. Taylor reveals to Zavala that Janet is pregnant. They are baited into chasing a reckless driver into an apartment complex where they are ambushed by the Curbside Gang. They fight their way into an alley where Taylor is shot in the chest. As Zavala desperately attends to his partner, the assassins arrive and shoot him several times in the back. Police backup eventually arrives, and the gangsters are killed after refusing to surrender.

Taylor survives, having been shielded by Zavala’s body. At Zavala’s funeral, Taylor tries to deliver a eulogy, but only manages to say a few words. In a flashback to the day of the shooting, Zavala recounts to Taylor a humorous story from the first time he and his wife slept together, before the two receive a call from dispatch.