The film opens with a striking sequence, presenting shots of white fabric tainted by blood poured deliberately by an unseen figure against the backdrop of the Alaskan wilderness. Weary detective Will Dormer arrives in the small town of Nightmute, Alaska, alongside his younger partner, Detective Happy Eckhart. They are greeted by the enthusiastic local detective, Ellie Burr, who idolizes Dormer's previous work, a fact that irks Eckhart.
Upon reaching the station, the trio inspects the body of Kay Connell, a seventeen-year-old whose murder they have been called in to investigate at the request of Dormer’s old friend, Police Chief Nyback. Dormer’s astute observations reveal that the murderer showed a certain respect for Kay's body, evident in her meticulously combed hair and trimmed nails, as well as her elegant dress. While searching through Kay's belongings, Dormer also finds pictures of her friend Tanya and boyfriend Randy, leading him to suspect that Kay had admirers. When he interrogates Randy, he learns that Kay had a secret that she never disclosed, a fact that complicates their understanding of the case.
In a local restaurant, tensions rise as Eckhart reveals that Dormer is under investigation for misconduct back in LA, leaving him furious and determined to prove his innocence. The friction between the two detectives escalates, leading Dormer to confront Eckhart and later connect with Burr, impressed by her detective aspirations. As they delve deeper into the investigation, Dormer’s insights deepen their understanding, but the shadows of doubt about his integrity loom large.
Things take a dark turn when Dormer accidentally shoots Eckhart during a high-stakes chase after the real murderer in a fog-laden forest. In a moment of horror, he discovers he has fatally shot his partner and swiftly decides to cover up the truth. Perez actions weigh heavily on him—haunted by guilt and the relentless brightness of the Alaskan day, he struggles with insomnia.
The narrative continues to unfold as Burr picks up the case regarding Eckhart's murder, leading Dormer into deeper entanglements—both with Burr, who begins to suspect him, and with the true killer, Walter Finch, who toys with Dormer’s deteriorating mental state. Their cat-and-mouse game intensifies as Dormer struggles to balance his efforts to regain control of the situation while preventing evidence of his own guilt from surfacing.
During interactions with Finch, Dormer's grip on reality slips, catalyzed by hallucinations and sleeplessness, forcing him to confront his past decisions—morally questionable actions he took with the belief that "the end justifies the means." Even as he attempts to manipulate the investigation to frame Randy for Kay's death, he finds himself ensnared in a web of deceit and regret.
In a climactic confrontation at Finch’s cabin, all the tension culminates in a deadly exchange where both men shoot each other, resulting in tragic outcomes for both. As Dormer lies dying, he faces the crucial moment of honesty with Burr, urging her to uphold the truth even at the cost of their camaraderie. The film concludes with Dormer finding peace in the wake of his internal and external chaos, prompting Burr to reflect on her mentor’s downfall as she stands at the lake, determined to honor his legacy.
> “Let me sleep.”
With this haunting finale, "Insomnia" leaves a lingering message about morality and the costs of pursuing justice at any cost.
