A murder has been committed in the basement of the Grand Hotel Majestic. Ms Petersen's body was indeed discovered in the staff locker rooms by a kitchen employee. Commissioner Maigret and Inspector Lucas are in charge of the case.

In these "cellars" where all the working people of a big hotel are busy, the head of the cafeteria, Donge, finds the corpse of Mrs. Petersen, a wealthy client. Investigation carried out by Maigret allows him to quote the husband of the victim, a Swede, Teddy, the son of Mme Petersen, his governess, a social dancer and Donge himself who is indeed Teddy's natural father. Will the child go to his real father or will he not leave the rich Petersen who adores him? The police enigma and the sentimental enigma are solved by Maigret.