A wealthy wine dealer's death doesn't bother his wife or "secretary."

A government minister asks Maigret to investigate when he becomes the victim of "dirty tricks".

Maigret is traveling by train on vacation to meet his wife and niece when he sees a man jump off the moving train. He follows and ends up in the hospital at Saint Clothilde with minor injuries. Then he finds out that there have been several unusual murders in the area, locally attributed to a "madman" and he begins an investigation with considerable resistance from local authorities.

Maigret is called to a farmhouse in Normandy; the owner has been killed. There he meets a 23-year-old woman named Felicie who is extremely defensive. She and Maigret keep up a barrage of unkind words the length of the story, it's wonderful to watch.