In the small fishing town of Nightmute, Alaska, 17-year-old Kay Connell is found murdered. LAPD detectives Will Dormer and Hap Eckhart are sent to assist the local police with their investigation, at the request of police chief Nyback, an old colleague of Dormer's. Ellie Burr, a young local detective who is also a fan of Dormer's investigative work, picks them up when they arrive. An LAPD Internal Affairs investigation is about to focus on Dormer—flying to Alaska, Eckhart reveals that he is going to provide testimony against Dormer in exchange for immunity, to which Dormer fears that many criminals whom he helped to convict using questionable evidence could go free if their cases are reopened.
Dormer attracts the murderer to the scene of the crime, but the suspect flees into the fog, shooting one of the police officers through the leg. Dormer spots a figure in the fog and fires with his backup weapon. Rushing to the fallen figure, Dormer picks up a .38 pistol the suspect has dropped. He then discovers that he has shot Eckhart. Because of Eckhart's pending testimony, Dormer thinks that Internal Affairs will never believe the shooting was an accident, so he claims that Eckhart was shot by the suspect. He doesn't mention he has the .38 pistol. Burr is put in charge of the shooting investigation, and her team finds the .38 caliber bullet that sliced the officer's leg. That night, Dormer walks to an alley and fires the .38 pistol into an animal carcass, then retrieves and cleans the bullet. At the morgue, the staffer hands him the bagged bullet retrieved from Eckhart's body but she is unfamiliar with its type. Dormer leaves and switches the .38 bullet for the 9mm slug from Eckhart's body.
Over the next few days, Dormer is plagued by insomnia, brought on by his guilt over killing Eckhart and further exacerbated by the perpetual daylight.
Dormer starts receiving anonymous phone calls from the killer, who claims to have witnessed Dormer kill his partner. When the police learn that Kay was a fan of local crime writer Walter Finch, Dormer breaks into Finch's apartment in the nearby village of Umkumiut. Finch arrives home, realizes the police are present, and evades Dormer after a chase. Dormer returns to Finch's apartment and plants the .38 to frame Finch.
Finch contacts Dormer and arranges a meeting on a ferry. Finch wants help in shifting suspicion to Kay's abusive boyfriend Randy Stetz and will stay silent about the Eckhart shooting in return. Dormer gives advice on handling police questioning. After Finch leaves Dormer on the ferry, he shows the detective a tape recorder he used to record the conversation.
Finch calls Dormer and tells him that Kay's death was "an accident" — he beat her to death in a fit of rage after she rejected his advances. The next day, Finch gives false testimony at the police station. When Finch claims Randy has a gun, Dormer realizes Finch has discovered his plant, and has hidden it at Randy's home. Randy is arrested when the gun is found at his house. Finch asks Burr to come to his lake house the next day, to collect letters indicating that Randy abused Kay.
Burr returns to the scene of Eckhart's death and finds a 9mm shell casing, which conflicts with the bullet type from Eckhart's body. She reads old case files from investigations Dormer was involved in and learns he has carried a 9mm, leading her to suspect that he shot Eckhart. Meanwhile, Dormer confides in the hotel owner, Rachel Clement about the Internal Affairs investigation: he fabricated evidence to help convict a pedophile he was certain was guilty of murdering a child, admitting that the ends justify the means in getting justice rather than seeking glory or being corrupt, though Clement does not judge nor turn him in since she is not an Alaska native.
Dormer learns that Burr has gone to Finch’s. He finds Kay's letters in Finch's apartment and realizes that Finch intends to kill Burr. He learns of Finch's lake house and rushes there. At the house, Finch knocks Burr unconscious just as Dormer arrives. Dormer is too disoriented from lack of sleep to fight off Finch. Burr revives and saves Dormer, while Finch escapes. Burr reveals she knows Dormer shot Eckhart, and he admits that he is no longer certain if it was an accident. From his shed, Finch shoots at them with a shotgun, and Burr returns fire while Dormer sneaks around to Finch's location. After a scuffle where the men inadvertently exchanged weapons, Finch shoots Dormer with the 9mm pistol, who shoots and kills Finch with the shotgun. Burr rushes to the aid of the fatally wounded Dormer and comforts him by affirming that Eckhart's shooting was accidental, then moves to throw away the 9mm shell casing to preserve Dormer's secret. Dormer stops Burr, however, telling her not to lose her way and tells her to let him sleep as he dies.Al Pacino as Detective Will Dormer
Robin Williams as Walter Finch
Hilary Swank as Detective Ellie Burr
Maura Tierney as Rachel Clement
Martin Donovan as Detective Hap Eckhart
Nicky Katt as Fred Duggar
Paul Dooley as Chief Charlie Nyback
Crystal Lowe as Kay Connell
Jay Brazeau as Francis
Larry Holden as Farrell Brooks
Kerry Sandomirsky as Trish Eckhart
Lorne Cardinal as Rich
Katharine Isabelle as Tanya Francke
Jonathan Jackson as Randy Stetz
Paula Shaw as the Coroner
Insomnia was filmed over a three month period from April to June, 2001. The opening aerial scene was filmed over the Columbia Glacier near Valdez, Alaska and the float plane approach was over the Portland Canal near Hyder, Alaska and Stewart, British Columbia. The town of Nightmute, Alaska was primarily filmed in/around Squamish, British Columbia, including the hotel/lodge, police station, high school, and the funeral cemetery scene. The scene where Will Dormer shoots his partner on the rocky beach in the fog was filmed at Clementine Creek in Indian Arm, outside of Vancouver, British Columbia. The village of Umkumuit, where Finch's apartment is located and where the log chase scene occurs, was filmed on Vancouver Island in Port Alberni, British Columbia. The waterfall road scene where Dormer is on his way to Finch's lake house and spins his car 180 degrees was shot in front of Bridal Veil Falls on the Richardson Highway near Valdez, Alaska. The final scene of the movie on the fictional Lake Kgun at Finch's lake house was filmed on the northwest end of Strohn Lake in Bear Glacier Provincial Park, just outside of Stewart, British Columbia. For this final scene, the film crew constructed Finch's lake house and dock from scratch and then disassembled and removed it after filming was completed in late June 2001.
Insomnia was well received by critics. Review aggregator Rotten Tomatoes gives the film a score of 92% based on a sample of 200 reviews, with a weighted mean score of 7.7/10. On Metacritic, the film holds an average score of 78 out of 100, based on 36 reviews.
Lou Lumenick of the New York Post gave the film an enthusiastic review, calling it a "four-course gourmet alternative to summer popcorn flicks, serving up the meatiest performances Al Pacino and Robin Williams have given in many years." Roger Ebert of the Chicago Sun-Times noted that "Unlike most remakes, the Nolan Insomnia is not a pale retread, but a re-examination of the material, like a new production of a good play."
Erik Skjoldbjærg, the director of the original film, said of Nolan's reinterpretation: "Well I haven't seen it for quite a while, but when I first saw it it was a very strange experience because it was quite close, stylistically, to the original. I felt lucky that it's such a well crafted, smart film and that it had a really good director handling it, because as a remake I think it did really well and it doesn't hurt any original if a remake is well done. So I felt I was lucky that Christopher Nolan took it upon himself to do it."
Robert Westbrook adapted the screenplay to novel form, which was published by Alex in May 2002.