Los Angeles, California, teacher Miss Tenny, and her four students—Julie, Pam, Tina, and Barbara, better known as Bobbie—are passengers on a chartered school bus, with Marvin at the wheel, headed to remote Native American ruins. Nearby, motorcyclist Pete has a flat tire while riding with his brother, Al. Jay Andrews, another motorcyclist, stops and fixes Pete’s inner tube. Although Al prefers to ride alone with his kid brother, Jay tags along, claiming Pete will need his help if the tire deflates before they find a service station. As the three pass the school bus, Pete and Jay wave to the girls. The bus and the three bikers pull into Gene Ammerman’s rural Mobil gas station. While Ammerman pumps gas into the bus, Jay talks with Julie, but she playfully insults him. As the bus pulls away, Ammerman accidentally spills gasoline on Al’s motorcycle and sparks an altercation. Al follows the old man inside, and as Ammerman slides under a car in his work bay, Al releases an air jack and kills him. Revving their bikes outside, Jay and Pete are unaware of the murder, and leave as soon as Al rejoins them. Meanwhile, the bus breaks down, and when the three bikers stop to help, Pete looks at the engine and tells Marvin he has a broken fuel pump. Julie apologizes to Jay for being harsh with him earlier. When Al leads Bobbie away from the others, Miss Tenny pulls her away from him, but Al threatens to go for help only if Bobbie can ride with him. The three bikers hook up the bus with ropes and pull it off the main road with their motorcycles. They stop at a lone house, but when Pete finds it deserted, Marvin gets angry that they pulled the bus to a remote spot. Al becomes abusive towards Miss Tenny after she resists his advances, and Marvin comes to her rescue. Al and Pete get on their motorcycles and chase Marvin. Pete knocks him down and Al runs him over, breaking Marvin’s neck. Al pulls his brother aside and warns they will go back to jail if the others identify them, so they must kill everybody. Jay whispers to Julie that their lives are in danger, and they must play along until they can escape. Al leads everyone into the house. When Bobbie tries to lure him away from the others, Al demands that she disrobe in front of everybody. Jay intervenes, but Al and Pete knock him unconscious and tie his hands. Then Al drags Miss Tenny into an adjoining room and rapes her. Bobbie romantically distracts Pete, while Julie loosens Jay’s bonds. Jay sneaks out the door and rides for help on his motorcycle, but Pete follows, kicks his bike, and sends Jay flying over a small cliff onto rocks below. At the house, as Al stares at the women and hums, Tina goes into the next room to tend to the traumatized Miss Tenny. When Pete returns with news that Jay is dead, Al rewards him by offering him any of the women he wants. Pete chooses Tina, but Miss Tenny has sent Tina for help. Al gives chase, catches her in the woods, and suffocates her. Afterward, he sleeps. By the time he returns to the house, Al tells everyone Tina got away. He grabs Bobbie and rapes her in front of the others. The next morning, Julie wants to go to the bathroom, and as Pete follows her outside, a rope with a noose drops from the roof and strangles him. Jay, only superficially hurt from his crash, climbs down and drags Pete’s body away, but Al steps out the door and pulls his knife. He and Jay fight until Miss Tenny picks up a stake from the ground and stabs him in the back, killing him. Jay gets on Pete’s motorcycle and goes for help. Realizing their ordeal is over, the teacher and her three students embrace.