Xavier Marton, the head of the toy department at the Grands Magasins du Louvre, a model train specialist, visits Maigret to say that he thinks his wife wants to poison him, but leaves while Maigret is out of the room. Later in the day the man's wife, Gisèle Marton, also visits Maigret, to tell her side of the story, which is that her husband is having delusions. Marton comes the next day, and agrees to have another examination with a psychiatrist. But he warns Maigret that if she poisons him, he'll shoot her before he dies. Meanwhile, Maigret has had both of them investigated, and finds that Gisèle's sister, Jenny, is living with them, and that Marton is apparently enamored of her. Gisèle, on the other hand, is apparently the lover of her employer, Mr. Harris. Maigret has the house watched during the night, and by morning Marton is dead, accidentally poisoned by Jenny, when Gisèle switched her cup of tea with her husband's. He had poisoned his own, with enough to make him sick, but not to kill him. Jenny thought he hadn't the nerve, so she added the poison to kill her sister.
This report prepared by Dana Samson