Inspector Maigret reopens an old case after a condemned prisoner mentions a past murder connected to a small riverside bar near the Seine. Curious, Maigret decides to investigate the place before going on holiday.
He discovers a quiet bar frequented by seemingly respectable people who hide complicated private lives filled with secrets, lies, affairs, and financial troubles. Beneath the calm atmosphere, tensions slowly emerge.
When a new murder occurs, Maigret carefully observes the suspects and connects the present events with the hidden past. Using patience and psychological insight, he eventually uncovers the truth.