At Oslo Police Headquarters, Crime Squad Chief Inspector Bjarne Møller receives a call about a body discovered in an attic apartment. The caretaker and a resident found the victim after water leaked into the apartment below. With most detectives on summer leave, Møller struggles to staff the case. He calls Beate Lønn (a forensics specialist) and then reviews the duty roster.

Møller assigns Inspector Tom Waaler, a reliable and skilled detective, to the case. Waller has been involved in two fatal shooting incidents during arrests, but both were ruled justified self-defense. He is on track to become the youngest Chief Inspector in Crime Squad history. Møller reluctantly decides to also assign Harry Hole, a talented but troubled detective who struggles with alcohol addiction. Harry has spent months obsessively investigating the murder of his colleague and close friend Ellen Gjelten. He recently presented Møller with conspiracy theories that included unsubstantiated accusations against Waaler, before disappearing for four weeks. Despite knowing the risks of pairing him with Waaler, Møller calls Harry’s number.

Harry Hole awakens from a nightmare featuring Ellen Gjelten’s distorted face. Møller calls with the assignment, telling Harry to report to the crime scene in the attic apartment. Harry walks to the crime scene where he meets Waaler. Beate Lønn arrives shortly thereafter and they discuss the case briefly. When Beate suggests Harry move on from his obsession with Waaler, Harry insists Waaler hurts people, alluding to bruises Beate once had during a brief relationship with him. She defends Waaler and says Harry imagines things. Harry refuses to enter the building’s elevator and takes the stairs instead.

Harry arrives at the crime scene in the attic apartment. Tom Waaler appears from the bedroom and coolly notes that Harry looks unwell. In the bathroom, Harry finds Camilla Loen’s body on the floor with a bullet hole in the forehead. Beate and Waaler calculate time of death at approximately 5:00 pm. Camilla’s index finger has been cleanly severed and is missing.

Harry interviews Vibeke and Anders on the fourth floor. They claim limited interaction with Camilla, knowing only that she worked in advertising design, and report no knowledge of boyfriends. When Anders demands to know if they’re in danger, Harry says the murderer is statistically more likely someone Camilla knew intimately. Vibeke explains she recognized the ceiling leak as blood because the lumps in her boiling water were coagulated albumin. Anders, who had tasted the lumps, turns pale. Harry notes that Camilla’s door had a double lock and security chains but was found unlocked, suggesting she opened the door to whoever killed her.

After leaving the crime scene, Harry drinks alone at Underwater, a nautical-themed pub. Møller calls, concerned that an officer threatened to report Harry for appearing intoxicated at the crime scene. Harry admits he doesn’t want to work with Waaler and tells Møller to remove him from the case or fire him.

Harry takes a taxi to the home of Rakel, his former girlfriend. He hopes to glimpse her or her son Oleg. Harry reflects on the previous winter, when they were in love and Rakel had hinted he should move in—before he became consumed with investigating Ellen Gjelten’s murder. He spent months obsessively pursuing the case, convinced that Waaler was behind Ellen’s death. Harry worked around the clock to build a case that Waaler is the smuggler known as “Prince,” shadowing Waaler and his associates.

Harry found a witness: Roy Kvinsvik, a former neo-Nazi turned Pentecostal convert. Kvinsvik claimed to have seen Waaler in a car with Sverre Olsen, Ellen’s alleged killer, on the night of the murder. Harry took his evidence to the head of police in late May, making a case for Waaler’s identity as Prince and arguing Waaler killed Ellen to silence her and then murdered Olsen after framing him for the crime. Rakel grew increasingly frustrated with Harry’s preoccupation and erratic behavior; in April, she ended the relationship.

Harry’s musings are interrupted when Beate calls to report they found the murder weapon—a Glock 23 with the serial number filed off—in the trash bin in Camilla’s apartment. More strangely, the pathologist found a small, reddish, star-shaped precious stone, possibly a diamond, lodged on top of Camilla’s eyeball. Harry insists it’s not his case and hangs up.

An unidentified narrator observes Harry leaving a bar and attempting to hail a taxi. The narrator reflects cryptically on water, thirst, and rejection, comparing Harry to a lost spirit unable to cross a river. The narrator contemplates the pain of being rejected while needing help, but also the possibility of lashing out at those who offer aid.

Four days after the murder, Harry shops for groceries and encounters Vibeke Knutsen at the checkout; they chat awkwardly, and she mentions police have been investigating all weekend but won’t share information with residents.

When Harry arrives home, Bjarne Møller is waiting on his doorstep. Shocked by Harry’s appearance, Møller confronts him about disappearing during the investigation. Inside the filthy, bottle-strewn apartment, Møller reveals he has written Harry’s dismissal papers, awaiting only the Chief Superintendent’s signature. He says he can no longer protect Harry, having risked his own career too many times, and calls Harry arrogant, selfish, and self-destructive. After Møller leaves, Harry falls asleep and recalls a meeting four weeks earlier.

At that meeting, Harry’s witness, Roy Kvinsvik, failed to appear. Harry arrived alone to explain that Kvinsvik had recanted, now claiming it wasn’t Waaler he’d seen with Olsen after all. The Chief Superintendent immediately closed the Ellen Gjelten case and warned Harry that any further pursuit of it or accusations against Waaler would result in dismissal and charges of false accusation. After the Chief left, Harry ordered his first drink in a long time. Since then, he has been steadily spiraling.