Domer is under investigation for planting evidence and his partner is going to testify. While tracking the murderer in Alaska, Domer "accidently" shoots his partner dead. The rest of the movie, Domer has to try and find the killer of the young girl and find a way to plant evidence to clear his name. Talking about the mise en scene of the film, Nolan has a very effective plot device that helps chiefly with the visual style of the film. Because it's constantly daylight and the protagonist has insomnia, the director puts the viewer through a series of disorienting scenes. The editing, lighting and stage director for the film really enhances that feeling. The film is shot with a very bleak atmosphere with a light of grey which serves two meanings..to me. It helps to put the viewer in the same disorienting feeling of Domer because the gray seems to blur everything together -- just like Domer's days in Alaska. The gray also servers to show the nature of the protagonist himself. He's a cop who plants evidence. He's a cop who shot another cop. He's also a cop looking for a killer. Not exactly the white knight but not the a black hearted killer either. He's on the line between light and dark...like most cops. LOL!
As Domer tries to go to sleep, we're there to see him struggle with the daylight practically, as he fights to get some shred of darkness back in his life. Which theme-wise is such an interesting aspect of the film. The character is a cop looking for a murderer, in a sense, bring light to the case. He shoots his partner and another cop is trying to uncover the truth. He's trying to get sleep and darkness is the only thing that will bring that about. A protagonist who is trying to bring about light while desperately searching for the dark.