Maigret goes to a small village after receiving a letter from the son of the schoolteacher. The schoolteacher is currently in prison awaiting trial for the murder of the village's postmistress. She was supposedly killed when he was out of the classroom for a few minutes one morning collecting graded essays from his house which is attached to the school. The schoolteacher is an outsider in a very insular community. Maigret investigates a collection of drunks and children to find the truth.