A group of naive young people has their carefree weekend in an isolated country house thrown into turmoil when one of them accidentally unleashes a mysterious and murderous creature trapped in the basement. As the demon begins to attack the couples, the blood-drenched body count mounts and, with it, more creatures with a taste for human flesh. The dazed young men and women soon mount their own desperate counter-attack, an attack that includes decapitations, dismemberment, spurting blood, flailing axes, and the kind of gore not normally associated with Swedish cinema!