'What was he doing there? A hundred times, in the middle of an investigation, he'd had the same feeling of helplessness or, rather, futility. He would find himself abruptly plunged into the lives of people he had never met before, and his job was to discover their most intimate secrets. This time, as it happened, it wasn't even his job. He was the one who had chosen to come, because a teacher had waited for him for hours in the Purgatory at the Police Judiciaire.'

When a school teacher from a small coastal town near La Rochelle asks Maigret to help prove he is innocent of murder, the Inspector returns with him to his insular community and finds the residents closing ranks to conceal the truth.