After middle-class, eighteen-year-old Barbara Bonney becomes involved with Eddie Rand, leader of the Vandals gang, Nan Baker, a member of the Black Widow gang, meets with Barbara to determine which one of them will be Rand's girlfriend. During their encounter, a fight ensues and Nan accidentally falls from a rooftop. Her body, along with Barbara's bracelet, is found in an alley by Helen and several other members of the Black Widows. Hel convinces the other members: Squirrel, Lorrie, May and Betty Kern, that Nan's death must be avenged. Certain that Barbara will seek help from Rand, Hel decides to offer Rand money to turn Barbara over to them. The members of the Black Widows then go to their respective homes to look for money or items they can barter. Upon returning home, Squirrel, an Hispanic girl also known as Eva, takes money from the cash register of her parents’ modest restaurant; Lorrie, a cruel psychotic, takes money sent by her father to support her younger sister, who lives in squalor and hunger; May fights with Janet, her older sister who is “dating” her much older employer; Hel finds her father in a tryst with a young woman while her mother is out working to support him; and Betty, the daughter of police officer Phil Kern, takes his revolver while he is asleep. Meanwhile, a very frightened Barbara has returned to her home but relates nothing of the evening’s events to her parents. The police, including Betty’s father, are summoned to the alley and Kern tells Det. Dunston, who is leading the investigation, that he recognizes the dead girl as a friend of his daughter. The Black Widows have gathered two hundred and sixteen dollars and the gun, but before going to the Vandals’ clubhouse, Hel decides to look for Barbara at her home. When her father answers the door, Barbara signals to him to say that she is not there, then slips out the back door. The gang sees her, however, and chases her until she hails a passing taxi to take her to the Vandals' clubhouse, where she tells the sadistic, unsympathetic Rand about the accident and begs for his help. Rand agrees to help her escape to Phoenix the next morning, but becomes worried when he learns that the Black Widows and their brother gang, The Tarantulas, may come to the clubhouse looking for Barbara and orders The Vandals to prepare for a rumble with them. Rand, to whom Barbara has simply been a plaything, tells her that she has done the worst thing anybody can do--she has stepped out of her class. When Hel and the others arrive quietly at the clubhouse, located in an auto wrecker’s yard, they see the Vandals preparing for a battle, and Hel sends Squirrel to summon The Tarantulas. Barbara is left inside, guarded by a psychotic gang member, Wally, who at first appears sympathetic to her, but then attempts to assault her. Meanwhile Kern and Dunston visit Barbara’s parents and after her mother informs them of her daughter’s involvement with Rand, Dunston arranges for several police units to converge on the auto wrecker’s yard. Just as the rumble begins, Barbara escapes from Wally by hitting him with a bottle, but is recaptured by the female members of The Vandals, who are then attacked by the Black Widows. Barbara again manages to escape and, while the police arrive and break up the fight, Rand runs off. Pursued by both the police and the Black Widows, Barbara hides in a warehouse where Rand finds her and offers to help. Barbara has learned her lesson, however, and after walking outside, collapses into Dunston’s arms. Despite Hel’s exhortations, Betty decides to leave the gang and returns the gun to her father, who embraces her. Squirrel also decides to quit and walks off into the night.