On a night soon after Woodstock has ended, a hippie-hating local farmer named Bert (Tige Andrews) 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 (Richard Webb) 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 (stuntman John "Bud" Cardos).
First, their dog is attacked and killed by the hairy horror, and later female band member Beckie (Belinda Balaski) is kidnapped by the creature and locked away in an abandoned building.
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.
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.