A retired colonel, who has been having an adulterous affair, is found dead, his head caved in, with the blacksmith's hammer left nearby. The police have several suspects, but can Father Brown, a visiting priest with a fondness for puzzles, solve the mystery?
Father Brown is staying as the guest of a retired colonel when his host is found dead, stabbed with a narrow blade, but no murder weapon. The police inspector gathers all the suspects together, but Father Brown has the answer.
Father Brown is called to investigate the beheading of a man, commited in a closed garden. Soon there seems to be some problems: How could the murderer get the body out of the garden? And how did the murderer get away? Soon after the first murder a head is discovered into the Seine. The solution to the murder is simple and brilliant.