The year is 1943 in Trondheim (Norway) and the Nazis are trying a new experiment to create "Super Soldiers", but it doesn't succeed. The Germans canceled the experiment and ordered the chemicals dumped in a lake in Sweden called Önsjön. During the mission, the Swedish military open fire at the German soldiers and the bottom of the lake became a Nazi grave. 30 years later, some teenagers are going to a music festival at Önsjön during their summer break. Party, beers and naked bathing - it seemed to be a great festival, until the dead began to walk again.