A dead and unknown woman is found in a canal. Police inspector Martin Beck becomes involved in the case. After several months the woman is identified. The police reconstruct the woman's last trip on the canal boat "Wilhelm Tham".

The police lieutenant Nyman is murdered in his hospital bed and Martin Beck and his colleagues have another murder to solve. They discover that Nyman was a very brutal and tough policemen who got many complaints about police-brutality. Particularly interesting is Åke Eriksson, whose wife died in police custody because of Nyman. Eriksson climbs up on a roof in central Stockholm and starts to shoot at people on the street below...

A routine mission ends up in a flaming inferno when a house suddenly explodes. It looks like a spectacular suicide attempt but the technical investigation reveals unexpected evidence. Beck and his men are soon on the tracks of a narcotic syndicate...

A famous industrialist is murdered at a restaurant in Malmoe. Police inspector Martin Beck in Stockholm gets the case. The suspects lead to people involved in illegal arms deals. But who was the biggest criminal, the murderer or the industrialist?

The unidentified dead body of a young woman is found in Göta kanal, Sweden's longest canal. At first there seem to be no clues to what happened, but thorough research by criminal inspector Martin Beck and his colleagues reveal that she is a librarian from Nebraska, USA. Helped by amateur footage from a cruising ship, they find a likely suspect but still need more evidence before they can arrest him.