It is Christmas and the Maigrets are looking forward to a quiet and peaceful day. But it seems that Father Christmas called the previous night on the little girl across the road, and showed a remarkable interest in the floor boards!
The tottering Lachaume mansion, with its attendant biscuit factory, had nothing to tempt a burglar. Who, then, was the killer of Leonard Lachaume? Maigret finds a sinister reason for the family's reluctance to talk.
Maigret comes into conflict with a defence lawyer intent on scoring points in the media at the police's expense. Mme Maigret has her own problems when she looks after a baby abandoned in a public park.