Barbara Svendsen, a 28-year-old receptionist at the law firm Halle, Thune & Wetterlid, reflects on how slowly time passes at work. Her boss has asked her to work late this Monday. She watches a bike courier with a covered face pass through reception.

A short, well-dressed man enters and requests water. Barbara goes to the ladies’ lavatory to fill a beaker. While waiting for the water to cool, she experiences a strange moment where time seems to accelerate, then return to normal. When the water finally runs cold, she fills the beaker.

A sound makes her look up. As she turns, she is startled by a man. He asks if he frightened her. She apologizes and bends to retrieve it. In the water’s reflection, she sees her own face and something moving beside it as time slows dramatically.

At 5:55 pm, Harry arrives at the law firm, which is now a crime scene. He parks in front of the television shop located nearby and heads to the ladies’ lavatory to inspect the body of Barbara Svendsen. Waaler and Harry inspect the body together, noting that she has been shot in the head. The murder weapon, a Czech pistol with a silencer, was left nearby. They discuss the known details: At 4:55, a visitor to the law firm (Andre Clausen) asked Barbara for a glass of water and she left the front desk to get it. She didn’t return and another woman who worked at the law firm found her dead in the bathroom at 5:11 (giving a precise window of time in which the murder occurred). No one was around to see Barbara or anyone else enter the bathroom (Harry and Waaler are not aware of the bicycle courier). Examining the body, Harry finds the left ring finger severed and a heart-shaped earring containing a small red diamond star. The earring was left by the killer.

Upon hearing these details later that evening, Møller concedes that they are dealing with a serial killer and tells Harry that the latter will spend his final weeks assisting Waaler with the case. Later that night, Beate meets with the diamond expert, who confirms that the two diamonds from the crime scenes originated in Sierra Leone and that she suspects they were cut in an Eastern European country, such as Czechoslovakia. Beate calls Harry with this information. Harry notes the gun was also Czech.

The killer addresses his sleeping beloved, touching her and telling her she has been found.

Harry wakes from a nightmare in which he was screaming. He recalls dreaming of two people in bed and shining a torch on them. Seeing dawn is still hours away, he forces himself back to sleep.

Early on Tuesday morning, Waaler begins a briefing, announcing he leads the investigation with Harry assisting. He introduces psychologist Ståle Aune, who presents on serial killer profiling. Aune explains that the FBI distinguishes between psychopaths and sociopaths, with sociopaths described as intelligent, successful individuals who blend into society. He outlines the six phases of serial killing, with early-phase killers exercising self-control and later-phase killers becoming increasingly brutal and careless.

Harry notes the escalating risk in victim selection: Camilla Loen was killed in her private flat, Lisbeth Barli kidnapped in daylight, and Barbara Svendsen killed in an occupied office building. This pattern suggests the killer may be losing control despite the careful ritualistic elements of the two known murders. Aune concludes they face a well-integrated sociopath whose trajectory remains unclear.

Waaler assigns tasks including re-interviewing witnesses. Harry interviews André Clausen (the client who asked Barbara for water), since he was the last person to see Barbara alive. As the interview ends, Clausen mentions seeing a courier leaving the building after Barbara had left the desk. Harry investigates and discovers no courier company made a delivery to the firm.

He brings Clausen back and learns the courier wore a helmet, sunglasses, and a white cloth over his mouth. Harry theorizes to Waaler that the killer is using a courier disguise to enter buildings unquestioned and then escaping quickly by bicycle. Waaler agrees and orders inquiries about courier sightings near all crime scenes.

Harry visits the church where he destroyed the window while Roy Kvinsvik hid inside. He wants to apologize for the damage. He chats with a Russian Orthodox pastor, who mentions that the star on the door is now hanging upside down, forming the shape of an inverted pentagram (a symbol for Satan in demonology). Harry seems intrigued by this information, mentioning that “I’ve seen this symbol just recently, but I can’t put my finger on where” (307).

The narrative shifts to Olaug Sivertsen, an elderly woman living in Villa Valle (a house near Oslo’s central train station). Olaug worked as a maid in the house during World War II (when Oslo was occupied by Nazi forces) and a German official lived in the house. He and Olaug had a sexual relationship, and she gave birth to their son after he left Norway at the end of the war. Now, decades later, she is lonely. A young woman named Ina lives as Olaug’s lodger and Olaug often tells Ina stories about her past. Ina confides that she is in a romantic relationship with an older man and that he has given her a gift, but she is not to open it until after they become engaged.

Meanwhile, at Møller’s office, the investigation team meets. Waaler reports the public appeal yielded no solid courier leads. There is also no forensic evidence from the crime scenes, and Aune (the psychologist) notes that it would be unusual for a serial killer to have no sexual motive. It seems increasingly certain that Lisbeth will not be found alive. Harry describes a sense that there is something significant to the locations where the crimes are taking place and observes that the diamonds have been cut into five-point stars, resembling pentagrams. He believes he has seen another pentagram somewhere at one of the crime scenes but can’t recall where. The police learn that a witness has recalled seeing a bicycle courier wearing a white mask near Camilla’s apartment on the day she died.

That evening, Harry finally remembers where he saw the pentagram. He drives to Camilla Loen’s empty flat to confirm: a pentagram has been carved into a wooden beam near the bed (Harry glimpsed this during his first visit to the crime scene). Wood shavings on the floor reveal that the carving is very recent. Harry lays on the bed in a reverie until Anders Nygård (the downstairs neighbor) appears and confronts him. Anders heard noises in the flat upstairs and came up to investigate. Anders and Harry go down to the latter’s flat, where Anders theorizes that the killer targets promiscuous women as divine judgment, then identifies the pentagram as a mare cross or devil’s star—a pagan symbol to ward off nightmares, derived from an Indo-Germanic root meaning death or murder.

At home, Harry finds a message from Rakel asking him to take Oleg swimming while she goes to an appointment. In bed, he experiences a vivid nightmare of a female demon.