Police, the tenth installment in Jo Nesbø's Harry Hole series, opens in Oslo with a loaded Russian Odessa pistol locked in a cupboard in the home of Rakel Fauke. Two of the gun's bullets killed Gusto Hanssen, a young thief, and three more struck Harry Hole, the ex-detective who served as a father figure to Rakel's son Oleg. Oleg was arrested for Gusto's murder but released when no weapon could be linked to him; the gun, if ever found, would implicate him. In a guarded hospital room, an unnamed patient lies in a coma. Isabelle Skøyen, Oslo's Councillor for Social Affairs, and Mikael Bellman, the newly appointed Chief of Police, both hope the patient never wakes, because he could expose their corrupt collaboration with drug lord Rudolf Asayev, who monopolized Oslo's narcotics market with an opioid called violin.
On a September evening, Erlend Vennesla, a retired detective from Kripos (Norway's national criminal investigation service), is bludgeoned to death near Lake Maridal. Beate Lønn, head of Krimteknisk (the forensic unit), recognizes the significance: The murder occurred at the exact location and date of an unsolved rape and murder Vennesla once investigated. Three months later, a second officer, Bertil Nilsen, is found impaled on a pole at Tryvann, the site and date of another unsolved case he worked. Someone is killing officers at the scenes of their old unsolved cases on matching anniversaries.
Bellman pressures Gunnar Hagen, head of Crime Squad, for results while protecting his own secrets. The comatose patient, actually Asayev, begins showing signs of consciousness, and Bellman and Skøyen arrange for an anaesthetist to eliminate him. Officer Anton Mittet, the hospital guard, is drugged through a tampered coffee capsule and falls asleep. The patient dies.
Katrine Bratt, a Bergen-based detective, uncovers a lead: A sex offender named Valentin Gjertsen was questioned about both original murders but had alibis from a woman named Irja Jacobsen, who has a history of false statements. When Katrine and Beate track down Irja, she admits she was coerced into lying for Valentin and identifies him through photographic evidence she found in his former flat, including his distinctive long, pointed cowboy boots. Although listed as dead in Ila Prison, Valentin actually killed a fellow prisoner, beat the corpse beyond recognition, forced a tattooist to copy his distinctive demon-face chest tattoo onto the body, and escaped.
Hagen assembles a secret unit to pursue the Valentin lead without Bellman's knowledge: Beate, forensics officer Bjørn Holm, Katrine, and psychologist Ståle Aune. They work from a windowless basement called the Boiler Room. Mittet then becomes the third victim, lured to the Drammen crime scene where René Kalsnes, a young man, was once murdered. The killer beats Mittet, binds him to his steering wheel, and rolls the car over a cliff. The murder replicates the Kalsnes killing closely, but Valentin was in prison when Kalsnes died, complicating the theory.
Harry Hole is introduced lecturing at PHS (Politihøyskolen, the Norwegian Police University College), where he appears healthy and sober. His trusted colleague Arnold Folkestad, a red-bearded man with a limp, co-lectures on murder investigation. Katrine and Beate separately try to recruit Harry, but he refuses, having promised Rakel he would never return to active police work. He cannot resist analyzing the case, however, and deduces how the killer lures victims: by phoning and posing as a detective reporting a new murder at the old crime scene. Harry identifies the next likely target, a house in Bergslia where the "Saw Man" once dismembered a girl, and proposes a trap. Bellman deploys Delta (the armed tactical unit), but the killer tests for police presence by sending a pizza delivery boy and never appears.
That same night, Beate is murdered and dismembered at her home, replicating the Saw Man case. Harry, devastated, joins the Boiler Room team as a civilian consultant. He also proposes to Rakel, who accepts. He pushes the team to reconsider motives, arguing the killer acts out of love rather than hatred, given the elaborate effort required to reconstruct each original crime. He identifies the Kalsnes case as the key anomaly: the only original murder involving a male victim with no sexual element, yet the only case linking all the murdered officers. Harry hypothesizes Kalsnes was killed by a policeman, citing a police baton found near the scene and a bullet matching police-issue weapons.
Ståle Aune, treating a patient who uses the alias "Paul Stavnes," glimpses the man's bare chest in a reflection and recognizes the demon-face tattoo: Stavnes is Valentin. Ståle alerts Harry, but Valentin takes Harry hostage at knifepoint and escapes. Delta raids Valentin's hotel too late, finding a football-match ticket stub from the night Vennesla was murdered. CCTV footage confirms Valentin was seated throughout the match, proving he did not act alone. A second killer must be involved.
Bjørn discovers that the Kalsnes evidence bullet matches Bellman's service pistol. Harry confronts Bellman, theorizing that Truls Berntsen, Bellman's lifelong enforcer, swapped the bullet as leverage. Bellman threatens Harry and disbands the group.
The breakthrough comes when Katrine discovers that a statistic Folkestad once cited to Harry does not exist. Folkestad fabricated it to steer Harry toward investigating Asayev's death, information only someone connected to the killings would possess. Further research reveals Folkestad and René Kalsnes were secret lovers, and Folkestad was the former Kripos colleague whom Berntsen savagely beat while Bellman watched, ending Folkestad's career. René was subsequently murdered by Berntsen on Bellman's orders to silence a blackmail threat. The case went uninvestigated because evidence of police involvement discouraged inquiry and René's lifestyle made him a low-priority victim. Folkestad became an avenger, targeting officers who failed in their duty.
Harry races to Hausmanns gate 92, where he finds Berntsen beaten and bound beside a pipe bomb. Harry seals them both inside a refrigerator moments before the explosion; both survive. Folkestad separately lures Bellman to the Rikshospital, sedates him, and removes one of his eyes with a scalpel as retribution. Hospital staff save Bellman's life.
Harry realizes Folkestad's Fiat is parked outside his house. Inside, Folkestad holds Rakel and Oleg at gunpoint. Harry texts Rakel a coded message referencing an old family trick: During their greeting embrace, she pulls the concealed Odessa from his belt. Harry lures Folkestad into the entryway. When Folkestad stands over Harry with his gun raised, Rakel fires a single shot through his temple.
The family faces a dilemma: If forensics examines the Odessa, the bullet will match Gusto Hanssen's murder and implicate Oleg. They transport Folkestad's body to Maridalen and stage it as a suicide. The case is officially closed. Ståle writes a report attributing Folkestad's crimes to paranoid schizophrenia, a diagnosis that ends scrutiny of institutional failures. The planted Odessa generates a false resolution to Gusto's case, protecting Oleg.
In June, Harry and Rakel marry at a small church in Oppsal, with Oleg as best man and a photograph of Beate in the witness chair. The novel's closing pages refuse to let the story rest. A police radio report of a murder at a building linked to Irja Jacobsen implies Valentin has silenced another witness. In the final scene, Ståle's daughter Aurora sits alone in a bathroom stall at a handball tournament and hears heavy footsteps. Beneath the door she sees the tips of long, pointed cowboy boots, the same boots linked to Valentin's crimes. The novel cuts to Harry on the church steps, eyes closed, feeling everything is at peace. Valentin Gjertsen remains at large.