In the sun-bleached deserts of the Southwestern United States, a brutal outlaw motorcycle gang known as the Satans roams, led by Anchor Russ Tamblyn. The gang’s crew includes Firewater John "Bud" Cardos, Acid Greydon Clark, Muscle William Bonner, Willie Robert Dix, Romeo Bobby Clark, and Gina Regina Carrol. One night they come upon two lovers—Johnny Martin Gary Kent and Tracy Jacqulin Cole—and unleash a brutal assault: they beat the boyfriend and rape the girl. After the atrocities, they kill both of them and hurl their car, with them inside, over a cliff.
Johnny Martin, a Vietnam veteran U.S. Marine, is hitchhiking and is picked up by former police officer Chuck Baldwin Scott Brady and his wife Nora Baldwin Evelyn Frank. Johnny—a Marine Police officer in the Corps—speaks of moving to Los Angeles to “live a little.” Tracy, a waitress, drives up in a red dune buggy to a diner where she works. She’s late and explains to her boss Lew Kent Taylor that she’s late because she was studying for a college class. Nora spots the cafe and tells her husband and Johnny to stop by for a meal. Johnny sits alone at the bar while Chuck and Nora share a table, thinking the Marine is keeping to himself. Johnny and Tracy strike up a quiet conversation about getting away from the desert town, and a spark begins to form between them.
The Satans roll into the cafe and demand service. Romeo harasses Tracy as she takes their order. Lew steps in, the tension eases, and the gang settles. Firewater chooses a song from the jukebox, and Gina glides into a go-go dance for Anchor, fueling his jealousy as he keeps a wary eye on the waitress. Lew shuts off the jukebox and tells the gang that this is “a place to eat” and not “a place to dance.” When one biker flirts with Chuck’s wife, she throws a drink in his face, and Chuck pulls a revolver, telling them to leave. The bikers knock Chuck unconscious and take his gun. The Satans pull Lew, Chuck, and Nora aside behind the cafe. Nora is raped, and Anchor explains why they hate cops. Anchor then kills the three of them as Johnny and Tracy escape in Tracy’s dune buggy, disabling Muscle and Romeo along the way.
The chase drives the couple deep into the isolated desert. Their dune buggy is damaged after they run over a couple of bikes, forcing Johnny and Tracy to trek on foot toward the nearest town. Meanwhile, the gang encounters a trio of female campers—Carol, Jan, and Lois—and they party with them for a while. Gina, consumed by jealousy, drives off and commits suicide by plummeting off a cliff, uttering Anchor’s name as she falls. Willie follows Johnny and Tracy but is bitten by a rattlesnake and dies. Firewater hunts for Willie, finds his body, and returns to find Acid playing Russian roulette with Chuck’s pistol while Anchor has gone even more unhinged, having murdered the three women. Firewater fights him, but Anchor overpowers him; Firewater staggers away, believing Anchor is still a threat. He eventually dies when a landslide traps him after a final confrontation with Johnny and Tracy.
The couple, exhausted but determined, eventually walks along the road. Anchor returns on the last working motorcycle, roaring that he is Satan and that Johnny must pay his dues as well. With a swift, desperate move, Johnny flicks a switchblade at the deranged leader, striking a fatal blow. Though wounded, Johnny still manages to ride the bike, and he and Tracy ride off toward the setting sun, leaving the desert’s danger behind them.
