Johnny (Marlon Brando), inarticulate leader of the Black Rebels Motorcycle Club, leads his followers into a town, looking for trouble. They burn up the streets, overturn cars, and insult townspeople. Town cop Harry (Robert Keith) fails to control the riders, or the rival gang that comes into town led by Chino (Lee Marvin). Johnny, attracted to Harry's daughter Kathie (Mary Murphy), is unable to explain himself to her or to understand her way of life. When his runaway motorcycle accidentally kills a man, Johnny is mobbed by the townspeople but saved by the county sheriff and order is restored. Cleared of a manslaughter charge with Mary's help, Johnny roars out of town.