When Maigret's fellow police officer Lognon is shot in Helsinki, he's forced to travel to Finland in order to investigate Lognon's shooting with the help of a local police officer Ari Vaara. But how are a Swedish art dealer, his French wife and a mysterious Brit involved in the shooting?
- A French police officer, Lognon, has been shot while on a mission to Helsinki, Finland. He has told no-one the reason for his mission and Maigret follows in his footsteps to Helsinki. He is met at the airport by Finnish police inspector Ari Vaara. Together they go to the hospital where Lognon has undergone surgery. Lognon is still unconscious and while they are there, an Englishman asks for him. The Englishman disappears before they can talk to him. After this, Maigret and Vaara go to the place where Lognon was shot. It is right in front of the house where Lognon was staying in the apartment of a Belgian call-girl, Paulette. Paulette rushed away after Lognon was shot and has not been seen since. Maigret's curiosity is caught by another house on the street, inhabited by wealthy Swedish art expert Gustav Junker. There is an exhibition ongoing and Maigret enters and talks to Junker. He has already been questioned by the Finnish police and didn't hear the shots. He introduces Maigret to his French wife, Mirella. Maigret and Vaara examine Paulette's and Lognon's apartment. From the window they see Mrs Junker leaving. They follow her car to a restaurant downtown where she meets with a lover. Afterwards she gives the lover a ride to the harbor where he leaves in a motorboat. Maigret checks into his hotel. Later he receives a visit from Mrs Junker who admits the adultery and begs of Maigret to keep it secret from her husband. The following day, Vaara takes Maigret to a cafe where Lognon spent all days watching Junker's house. A sea captain in the same cafe tells Maigret that Junker often received visits from prostitutes. Maigret calls on Junker with the pretext of being interested in his art, but starts to ask questions about the prostitutes. Junker shamefully admits his habit. Back at the hotel, Maigret receives a phone call from Paulette. He and Vaara travel to the hotel from which she called, only to find that she has already left. At night they return to the cafe and see a drunken man being dragged out of the Junker estate. Maigret calls upon Junker again. Junker claims that the drunkard was a student. When Maigret hears that Mrs Junker is painting in her studio, he requests to see her. The studio is visible from Paulette's apartment. In the studio he finds a locked room. At first the Junkers refuse to open the room, claiming that the key has been lost. When they finally give in, Maigret finds the room filled with paintings of nude women. Junker claims that they were painted a long time ago by a Russian refugee. The third day, Vaara's captain gives Maigret a scolding since he has received complaints from the Swedish ambassador. They are interrupted by a message that a dead body has been found in the harbor. It turns out to be the man dragged out of Junker's house. Meanwhile, Paulette has been found in a hospital and Maigret visits her. After this he confronts Junker. His wife escapes to the port, but is followed by Vaara. She and her lover are brought to the police station together with Junker. Maigret discloses the story: Mirella and her lover, the Englishman Hobson, have kept the Russian artist Ivan at Junker's house. Ivan is a genius who can paint in the style of any master. His forgeries were verified by Junker as real.