On a night soon after Woodstock has ended, a hippie-hating local farmer named Bert heads out in a drunken rage to the rubbish strewn festival site and gets his chromosomes scrambled when he receives a massive jolt of electricity trying to smash one of the still standing stages that, unfortunately for him, is still attached to the power lines. Family physician Dr. Marlow bandages his burns and says he will recover if he gets plenty of bed rest, but during the very next electrical storm he transforms into a shaggy, snarling werewolf with massive lupine jaws. A struggling young hippierock band shows up at the Woodstock site, intending to record an album on the stage where famous rock icons had performed, and quickly begin to have run-ins with not only the local police but also the hippie-hating werewolf. First, their dog is attacked and killed by the hairy horror, and later female band member Beckie is kidnapped by the creature and locked away in an abandoned building. The farmer keeps transforming during electrical storms and nobody realizes what's going on until one stormy night Bert changes into his furry, fang-faced form in front of his wife. Up until this point local lawman Lt. Martino thinks it has all been the work of some leftover drugged-out hippie, but "big city detectives" Moody and Kendy sent from Los Angeles to monitor the goings-on at Woodstock had already figured out a werewolf was involved in all these murders, and now that they know who the werewolf is they form a plan of attack which involves luring the creature out into the open with the one the thing it hates most, rock music, and then confusing it long enough to tranquilize it and capture it. Despite the best and loudest efforts of Beckie's bandmates the plan fails, and Bert, now permanently transformed into a monstrous man-beast even during storm-free daylight hours, runs back to the abandoned building, grabs his terrified hostage and escapes with her by stealing a convenient dune buggy with the police in hot pursuit. They end up at a power station where Moody chases the werewolf up the metalwork. His partner Kendy arrives with a newly made silver bullet, and as Bert attempts to kill the detective at the top of the station, Martino shoots at it from the ground, and the werewolf falls to his death.
