Maigret's expected Saturday evening in January, of a meal and watching his recently installed television, is suspended when Léonard Planchon, a nervous man with a hare lip, visits him.

In a long conversation, Planchon, who has a decorating business, tells Maigret how he met his wife, and about Roger Prou, an employee.

On Sunday morning Maigret phones Headquarters and asks if there are any reports from the 18th arrondissement of Paris, where Planchon lives, thinking there might be a murder.

In the afternoon, Maigret and his wife take a walk past Planchon's home; on Monday he gets colleagues, pretending to be council surveyors, to look round the house.

Although Maigret is not sure what sort of case he is investigating, he manages to get permission from the Deputy Prosecutor to interview Planchon's employees.