Inspector Maigret misses his revolver, a prized piece given to him by the FBI. His wife suspects that the young man who had been in their apartment that morning had stolen the gun. Later, it turns out that this visitor is the son of a certain Baron Lagrange, whom Maigret had invited for the evening together with his family doctor and who wanted to excuse his father. Lagrange is not available for Maigret, supposedly he is sick in bed. During his visit, the inspector accidentally learns that Lagrange and a cab driver had dragged a large suitcase out of the house the previous night. This suitcase is found at the luggage storage in the Gare du Nord - a dead man is lying inside. The clues lead to London ... Based on the 40th novel in the Maigret series: 'Le revolver de Maigret' (1952). In the German-speaking world, the novel was published as 'Maigret and his revolver'.