Brenda, a rebellious high-school student, spends an evening on Hollywood Boulevard with her group of friends known as the Satins: Rachel, Stella, Francine, Stevie, and Maria. Accompanying them is Brenda's younger, innocent deaf-mute sister, Heather, whom Brenda has grown extremely protective of since their father's death. A reckless drug-dealing gang called the Scars—Jake, Vince, Red, and Fargo—nearly run the girls down on a street corner in Jake's convertible, forcing Heather to hit the ground. In a fit of impulse, the girls steal the convertible, fill it with garbage, and abandon it on the street.
Jake stalks the Satins at their high school, wins the naive Heather's trust, and, with his cohorts, brutalizes and rapes her. After school, Heather is found unconscious in the locker room and is hospitalized in a coma. That night, the girls migrate to a local disco where they encounter the Scars, and a fight erupts after Fargo harasses the pregnant Francine.
After Francine has a dress fitting for her impending wedding, she is stalked by the Scars who chase her through an industrial section of the city before Jake murders her by throwing her off a viaduct spanning the Los Angeles River. The crime enrages Vince, the only member who expresses remorse for their actions, and he cuts ties with the Scars. Later, Brenda encounters Vince apologizing to the comatose Heather in her hospital room. That night, Brenda confronts Vince at his house at knifepoint, where he admits the Scars have murdered Francine.
Seeking vengeance, an enraged Brenda visits a weapons store, where she purchases a crossbow and several bear traps. She ventures into a sparsely populated section of the city, where she locates the Scars near an abandoned textiles warehouse. Brenda taunts Fargo and Red, luring them into the warehouse, where she kills Fargo by shooting him through the neck with the crossbow, before dispatching Red by snapping a bear trap over his throat. Meanwhile, Jake kills Vince in a nearby alley by striking him with his car.
Jake finds Fargo and Red's corpses in the warehouse. He attempts to shoot Brenda with a pistol, but she incapacitates him by shooting him with the crossbow, and trapping him with a rope around his ankles which hangs him upside down. Brenda tortures the defenseless Jake by stabbing him with a hunting knife, but he manages to free himself and attacks her. Jake chases Brenda, cornering her inside a paint store. While the store's burglar alarm blares, Brenda douses Jake with paint before setting him on fire. Police arrive as the engulfed Jake stumbles out of the store and dies.
Some time later, Brenda, Heather, and the surviving members of the Satins visit Francine's grave. > "At least we made things right." > "No, Brenda, you made things right."
