Fred Morrow, a Los Angeles real estate agent, gets off the freeway in an East L.A. neighborhood and makes a phone call at a café frequented by teenagers. While on the phone, he witnesses the fatal stabbing of Emelio Sanchez by gang leader William L. Tompkins, known as "Cowboy," who found Emelio dancing with his flirtatious girl friend, Ruby. When none of the many neighborhood witnesses come forward to testify to the police, Fred steps forward and relates Emelio's dying words, "Cowboy did it." At police headquarters, Fred identifies Cowboy's mug shot to Detective Rafael Torno, who is fearful he will lose Fred's cooperation once he discovers the possible consequences of being the only witness to the murder. At the gang's hangout in a garage, Cowboy becomes frantic when he learns from a newspaper article that Emelio has died and that the district attorney has a mystery witness. After Ruby relates that she saw police officer Hurley write down Fred's name and address, "Muggles," a beat-talking drug addict, comes up with a plan to get Hurley's notebook. While Hurley is making his neighborhood rounds, "Apple," an African-American member of the gang, and the only one who was visibly pained when Emelio was stabbed, attacks Ruby and takes her purse, then runs into an alley and hides. When Hurley follows, Cowboy knocks him over the head with a pipe, and they take Hurley's notebook and gun. Cowboy calls Fred's home and learns from his young daughter that he and his wife Ann have gone to the supermarket. Apple tries to talk Cowboy out of killing Fred, but Cowboy orders him to go away and keep his mouth shut. The gang ram Fred and Ann in their car after they leave the supermarket and push them through an intersection, nearly causing an accident. Muggles then pulls a gun on Ann, while Cowboy warns Fred to tear up the affidavit. Fred reports the incident to Torno, who arranges police protection for the Morrows. That evening, Cowboy phones and gives Fred until midnight to rip up the affidavit, or else, he says, his wife and children will die. When a note tied to a rock is thrown through their living room window, Fred prepares to take his crying children and Ann to a motel, but they find that their car has been vandalized and the tires slashed. When the police arrive, Fred expresses his anger. Meanwhile, Torno goes to see Apple, whom he once arrested with Cowboy, but Apple denies being with Cowboy that day. At ten minutes to twelve, Cowboy phones Fred, who tells him to go to hell. Ann becomes hysterical, yelling that the gang will slit their throats. As Cowboy and the gang prepare to torch the Morrows' house with kerosene, Apple comes to the garage asking for money so that he can leave town. Torno and the police, who have followed Apple, surprise the gang, but Cowboy escapes in a stolen Jaguar and leads the police on a chase through Los Angeles streets and freeways. After eluding them by turning the wrong way up an exit ramp, Cowboy drives over an embankment. Torno catches him on foot and subdues him. Meanwhile, Apple's mother interrupts him as he is packing to tell him that Muggles, Ruby and another gang member, "Magician," have come for him. When Apple tells his mother that he is leaving to take a job in San Diego, she indignantly says that although she scrubs floors for a living, she is not a fool, but he asks her to believe him and she says she does. Magician, a racist, hits Apple, whom they accuse of purposely leading the police to the garage. When Muggles pulls a gun on him, Ruby takes it away, saying she believes Apple. That night, Fred identifies Cowboy through a one-way glass at the police station. The next day, Ruby decides to kidnap the Morrows' children. Apple is aghast, but the others agree to her plan. As Fred is about to testify, Ruby attacks Ann in the courthouse hallway. When Fred learns about the attack, he testifies he was mistaken in his identification of Cowboy. Meanwhile, on the playground at the children's school, Muggles locates the Morrows' son and pulls a gun. Apple hits his arm as Muggles shoots, wounding the boy. As they drive off, Apple rolls out of the moving car. Muggles sees him run to Fred's house and tells Cowboy, now free on bail. When Fred finds Apple at the Morrow home, Fred slugs him and makes a racist remark, then tries to provoke him into a fight. Apple asks help to reach Torno, but Fred taunts him, saying facetiously that he should tell the newspapers he is underprivileged, fatherless, hungry, lonely or mentally ill, so that they will protect him. When Fred calls him "boy," Apple is about to leave, when the gang shows up. Cowboy pulls a switchblade, and Fred tries to protect Apple. The gang make a circle around the two, and Cowboy asks Fred why he is risking his life for a "nigger." After another racist remark, they fight, and Fred knocks the knife away. Torno then arrives with the police, who capture the gang. Fred tells him that now he has two key witnesses.
