In a small town in northern Norway, renowned Swedish detective Jonas Engström arrives to assist the local police in solving the murder of a teenage girl. Battling intense insomnia caused by the region's perpetual daylight, Engström's judgement becomes increasingly impaired. As he investigates the crime, he makes a crucial error during a foggy stakeout, and in an attempt to cover it up, he finds himself embroiled in a web of deceit and moral ambiguity. His professional integrity is called into question as he manipulates evidence and witnesses in a desperate attempt to conceal his mistake.

The relentless daylight and his own guilt exacerbate Engström's insomnia, leading him into a downward spiral of paranoia and confusion. He becomes obsessed with catching the girl's killer, yet his own actions make him question his moral compass and the line between right and wrong. The investigation takes unexpected turns, drawing Engström deeper into a labyrinth of lies and corruption. Ultimately, the strain of sleeplessness and his own ethical compromises push him to the brink, leaving his future hanging in the balance.