Lady Felicia is hosting John Langton, the Earl of Frome and the bishop is demanding that Father Brown organizes a service which will impress the peer. At a party for the earl an unwelcome guest is his profligate cousin Basil Urquhart and when the earl's baby son is kidnapped, Basil is a prime suspect, along with the earl's valet Parkin, who kept his marriage a secret. The child is returned unharmed but when Parkin's wife turns up Father Brown deduces that she has been the victim of a crime herself years earlier, which helps solve the mystery of the kidnapping. Come Christmas day Michael, a tramp who has been sleeping in the church, comes to the aid of the service, making it a success.