The brother of the vicar of the village where Father Brown has his parish church is a cad and a wastrel. When he's found near the church tower with his head smashed by a very small hammer, the local blacksmith is the first suspect, but it's his wife who confesses the murder!

When an alcoholic woman is found drowned near her home, Father Brown suspects murder, although the police think it's an accident.

A poet hangs himself in his locked conservatory. Father Brown thinks that it was not a suicide, but a murder.

Lady Felicia finds an unconscious, stripped man in a tree, apparently having been thrown from a train passing on the viaduct above.

Susie is fallen under the spell of the charismatic leader of a sect. When his wife dies in a suspicious accident, Father Brown intervenes but the prophet has a cast-iron alibi.

When two nuns are murdered, Father Brown investigates in the convent with the help of a young nun, very keen on detective fiction.

A radioactive girl is missing and only Father Brown can find the one responsible for her disappearance.

When Clarence Clifton is murdered at a charity treasure hunt, its organizer Professor Galloway believes he was the intended victim as they wore identical fancy dress. Daniel Walsh, whose father had recently been killed by Lady Margaret's car (the professor's wife), is the chief suspect and disappears. Then Lady Margaret is killed after sacking servant Thomas Dilcott, secret lover of her daughter Lucia. The villagers suspect Daniel but Father Brown looks closer to home for the solution.

At a fête to raise funds for a Polish school unpleasant mayor William Knight is electrocuted by a microphone. Valentine arrests his long suffering wife Eleanor after a screwdriver is found in her handbag but there are plenty of other suspects, including his young daughter and the secretary he sacked after their affair was discovered, whilst he was also accused of bribery and corruption. As Father Brown solves the mystery a magician at the fête turns out to be the husband,presumed dead, of his housekeeper Mrs McCarthy, who walked out on her decades earlier. Now dying he wants to return to her but she refuses him.

When the notorious thief Flambeau declares his intention to steal a valuable blue cross from the church, Father Brown, against the advice of Valentine, decides to take it to safety to Newbury abbey by train. He meets a trio of fellow passengers, one of which he is sure is the thief but his efforts to flush him out lead to the theft of the cross. Facing dismissal for his rash action the Father agrees to meet with Flambeau and do a deal to return the artefact.