Will Dormer (AL PACINO) and Hap Eckhart (MARTIN DONOVAN) are LAPD detectives who've been sent to the remote Alaskan town of Nightmute to investigate the murder of 17-year-old Kay Connell (CRYSTAL LOWE). One reason for that is due to Will being a legend in the field of homicide investigation, a point that draws young local cop Ellie Burr (HILARY SWANK) to him. The other, however, is that both cops are under investigation by their Internal Affairs department, and Will is none too happy that Hap is prepared to cooperate with them.
Nevertheless, the two set out to work with Chief Nyback (PAUL DOOLEY) and his team to figure out who killed the young woman. The obvious suspect is her abusive boyfriend, Randy Stetz (JONATHAN JACKSON), particularly since he's now seeing Kay's former best friend, Tanya Francke (KATHERINE ISABELLE).
Yet, Will senses that there's more to the case than that, and begins to believe that local novelist Walter Finch (ROBIN WILLIAMS) might somehow be involved. Things become more complicated, however, when Hap is shot and killed and Will suffers from a bout of insomnia in this summer land where the sun never sets. As he tries to deal with both of those issues, he's then lured into a dangerous psychological game of cat and mouse with Walter, all while trying to keep his sanity so that he can solve the case.