In this delightful tale, an Eastern Prince arrives in England with some family jewels which he's having reset as a gift for his fiancee. However, the Prince also has a mistress; she asks to wear one particularly enchanting piece that features a huge ruby, and then promptly disapppears with it. Poirot discovers a connection with a house party at the home of Colonel and Mrs. Lacey, and in order to pursue his investigation an invitation is procured for him to the Laceys', ostensibly to enjoy an old-fashioned Christmas. With deft skill and the workings of his 'little grey cells', Poirot brings this case to a satisfying end, starring John Moffat as Hercule Poirot, with Donald Sinden and Sian Phillips as Colonel and Mrs. Lacey.