Sent to a Norwegian town to help with a homicide investigation, tenacious detective Jonas Engström (Stellan Skarsgård) and his partner set a trap for the suspect. But the fog-shrouded stakeout goes awry: Engström mistakenly shoots his partner, then covers his tracks -- forgetting that the suspect witnessed the killing. Soon, Engström's guilty conscience and insomnia in the land of the midnight sun lead to a downward spiral into chaos.