At 3:10 a.m., police, shooting from the rooftops, gun down six heavily armed gang members. Later, four multi-racial Los Angeles gang warlords meet in a room full of stolen automatic weapons. Each man cuts his arm and bleeds in a glass bowl. That afternoon, Ethan Bishop is disappointed to learn that his first night as a police lieutenant will be spent supervising the decommissioning of the Anderson precinct, aka Precinct 13. At 5:11 p.m., special agent Starker arrives at Los Cruces prison to transport three prisoners to Sonora, California. The warden introduces him to the convicts: Wells, a muscular African-American man; Cornell, an ill and skinny white man; and Napoleon Wilson, a death row inmate, shackled to a chair. The warden knocks Wilson off the chair, then leads him outside where Wilson wraps his chains around the Warden’s legs and pulls him off his feet. Meanwhile, Lawson and his young daughter, Kathy, drive by the Anderson precinct looking for Kathy’s nanny’s house. They pass the gang leaders, who screw silencers onto their automatic weapons. Later, Bishop arrives at Anderson and meets his skeleton crew: Julie, a switchboard operator; Leigh, a secretary; and Chaney, an elderly police sergeant. Bishop is briefed that only two shotguns are left in the precinct and he will be relieved at 4 a.m.; the precinct will close at 10 a.m. Meanwhile, on the prison bus, Cornell has a coughing fit so bad that Starker orders the driver to go to the nearest police precinct. At 6:18 p.m., Lawson stops at a phone booth, while Kathy runs over to an ice cream truck. The ice cream driver is distracted by a black car that keeps circling the block. After Kathy skips away with her ice cream, the driver is pulled out of the truck by the white gang leader. Realizing she got the wrong flavor, Kathy comes back to the truck and is shot by the gang leader, who then fatally shoots the driver. Lawson finishes his call and sees Kathy lying by the truck. Cradling Kathy’s body, Lawson sees the black car drive away and the dying driver says there is a gun under the dashboard. Meanwhile, the police bus arrives at Anderson, and a reluctant Bishop allows Starker to use the holding cells, while he calls a doctor. At 7 p.m., Lawson chases Kathy’s killers until they jump out of their car and run. Lawson kills the white gang leader, then realizes he is out of bullets, and runs to Anderson precinct. Collapsing at the front desk, Lawson is so traumatized that he can only say he is being followed. Ethan Bishop puts Lawson into the Captain’s office and tries to call a doctor, but the phones and the lights go dead. Bishop at first believes it is an outside power failure, but the streetlights remain on. Special agent Starker decides to leave; however, when Chaney and Bishop step outside, Chaney is shot dead. Bishop runs back inside, and rushes to the holding cells, but is too late to prevent Starker, the guards and Cornell from being gunned down as they step outside. Napoleon Wilson steals Starker’s keys, but Bishop makes Starker give them to him after he gets Wilson and Wells back inside and into the holding cells. Salvos of bullets greet Bishop as he returns to the lobby. When the firing stops, he looks outside and sees everyone is gone. Leigh explains there is no rear exit to the building, and all the surrounding buildings are abandoned. As Bishop gives her his revolver and orders her to watch the windows, the gang leaders throw the glass bowl of blood at the door. Sobbing, Julie pleads with Bishop to give the gang Lawson, but he refuses. The shooting resumes, and Bishop hands Leigh the cell keys, ordering her to free the prisoners. As she opens the cells, a thug breaks down the outside door and shoots her in the arm. She smashes the man in the face with the key ring and opens the cell. With Wells and Wilson, she fights her way back to the lobby and barricades the door. Other gang members smash through the windows. Bishop tosses Wilson a shotgun while Wells retrieves a gun from a slain gang member. When the fighting is over, they discover Julie is dead. Bishop notices an acetylene tank and exclaims that they could have been blown to pieces. Looking outside, Bishop sees that all the corpses have been removed to make it seem like nothing has happened. When Wells informs them he is leaving, Bishop stands in his way and Wells pulls his gun. Leigh steps between them, telling Wells he will be gunned down if he goes outside, then notices Wells is out of bullets. A quick check shows they have only eight bullets left. Remembering that a tunnel runs from the basement to a manhole in the parking lot, Leigh explains someone could crawl out, and go for help. The two prisoners play a game to decide who goes out and Wells loses. He crawls out, hotwires a car and drives off. When Wells stops at a phone booth, a gang member sits up in the back seat and shoots him in the head. Wilson recommends they retreat to the basement as it is easier to defend. As they descend the stairs, Leigh asks Wilson why he did not try to escape and Wilson replies that there are only two things a man never leaves behind, one is a helpless man, but he does not say what the second is. Bishop wraps some flares around the acetylene tank, explaining that when the gang attacks, he will shoot the flares to detonate the tank. He and Wilson will use a huge metal sign to shield them from the blast. Meanwhile, policemen patrolling the neighborhood call for backup when they find a dead telephone repairman hanging from a pole. Back at Precinct 13, the gang attacks, but Wilson and Bishop use clubs to force them back. Leigh shoots a man coming in from the sewer. When the hall is full, Bishop shoots the tank with his final bullet and it explodes. As the smoke clears, police enter to find Wilson, Leigh, Bishop and Lawson still alive. When a policeman tries to handcuff Wilson, Ethan Bishop pushes him away and says it will be a privilege if Wilson will walk out with him. The two leave the smoking basement.