In a closed mine in northern Sweden, Lars Ruud is leading the work of creating the world's largest final repository of nuclear waste. The project is delayed and activists are trying to stop the opening. One night, the guard Oskar shoots an intruder in the area. Shortly afterwards, a mysterious explosion occurs that kills three people in Lars' team. His closest colleague Helen survives but does not remember much of the incident. When Lars goes down into the mine again, he discovers something very strange.