When Professor Gerald Smaill, an American archaeologist, discovers a golden Byzantine cross in cave in Crete, a disembodied voice threatens him with death.
Father Brown and Flambeau come to the aid of Christabel Carstairs, the daughter of a famous coin collector, when she is shadowed by a mysterious figure dressed in a disguise and bent on blackmail.
After an heiress makes her will out to the leader of a bogus religious cult and mysteriously falls to her death, Brown finds that he is the charlatan's alibi.
A wealthy landowner in the West Country confesses to Father Brown that his adopted son has coerced him into dabbling into occultism in order to extend his life.
After a rash of robberies, the evidence implicates a gentle beekeeper as the notorious jewel thief whom the press has dubbed Michael Moonshine. Father Brown keeps faith in his friend, however, and unmasks the real murderer.
The search for a runaway girl leads Father Brown and his friend Flambeau to a struggling theatre company, replete with backstage gossip, ambitious actors, tempermental divas, mysterious visitors, and murder.
A decapitated man is found in a garden, and an eccentric American millionaire is suspected when he disappears. But then his severed head is discovered.