Maigret goes to Givet, on the Meuse, the Belgian border, at the request of Anna Peeters, who has come to Paris with a letter of reference from Mrs. Maigret's cousin in Nancy. The Peeters have a shop, the Épicerie Peeters, catering especially to the Belgian barges, and besides Anna there is a son, Joseph Peeters, a law student, and a daughter, Maria Peeters, a teacher in the Ursuline school. Joseph is said to have fathered a son, Jojo, with Germaine Piedboeuf, although he's always been expected to marry his cousin, Marguerite Van de Weert. Now Germaine has disappeared, last seen going to the Peeters to get her monthly allowance for the boy, and the Peeters are suspected of having done away with her. But there's no body. The inspector from Nancy, Machère, also believes the Peeters guilty.
Germaine has a brother, Gérard Piedboeuf, and he'd had a brief affair with Anna, Maigret learns. Then there's a barge man, Gustave Cassin, who first claims to have seen someone throwing a body into the Meuse, then seems to deny it. Maigret visits his barge, and finds Germaine's coat and a hammer. Then her body is found 50 miles downstream – she'd been killed by hammer blows to the head. Finally Cassin disappears, leaving a note of a false suicide, and he is considered by everybody the killer. But Maigret, with no official capacity in the case, confronts Anna. As he had figured out, she'd killed Germaine, in order to protect her brother's happiness - that is, so that he could marry Marguerite. She enlisted the aid of Joseph and hidden the body, finally throwing it in the river. Gérard had paid Cassin, who said he had evidence, but then Cassin went to Anna, got more money, and disappeared. Officially, Cassin was assumed guilty.
This report prepared by Dana Samson