[1] A veteran Swedish policeman named Stig Nyman is brutally murdered, bludgeoned and eviscerated with a bayonet while being treated for a secret illness at a Stockholm hospital.

Although his colleagues generally disliked Nyman and had been aware of his behavior, the police force's esprit de corps had suppressed complaints about him and prevented any reprisals.

The investigation proceeds, and finally Beck and his team find a trail that leads to the murderer, who turns out to be an ex-policeman named Eriksson.

Eriksson's wife Marja had diabetes and went out to buy insulin before passing out from her illness; Nyman found her unconscious on the street and instead of bringing in medical treatment, had her arrested for public intoxication and placed in a holding cell.

A group that includes Larsson, Hult (a stone-faced officer who was one of the few members of the force who was close friends to Nyman, and who resolves to avenge his death), special operations soldiers and a civilian volunteer with his own firearms on hand use explosives to blast to the roof where Eriksson is hiding.

The actor Carl-Gustaf Lindstedt was picked for the part as the policeman Beck after Wideberg had seen him with a serious face in a talk show not knowing he was on air.