The men of the Paris canals are tough and resentful of interference. So Maigret finds when he comes to investigate the mysterious accident to Emile Ducrau, and the dangerous web of relationships that caused it.
The trial of Gaston Meurant is about to start. He is charged with double murder and there seems little doubt of what the verdict will be. Can Maigret uncovers new evidence likely to save Meurant's life?