Hercule Poirot is excited at the prospect of meeting one of his idols, Belgian actress Marie Marvelle. When they meet, Ms Marvelle informs Poirot that she has been receiving letters, threatening to steal her priceless diamond, the Western Star. Upon research, Poirot discovers that there is also an Eastern Star diamond and the two form a set. The Eastern Star is currently owned by Lady Yardly. Within days, Lady Yardly comes to Poirot stating that she too is receiving threats of theft. Poirot visits Lord and Lady Yardly at their estate and, while there, the Eastern Star is stolen. The next morning, the Western Star is stolen out of Ms Marvelle's hotel by a man impersonating her husband.
Quite interesting but ultimately there are not that many surprises. The villains of the piece are fairly obvious. Moreover, the ending is a bit of a damp squib and is more about sentimentality than justice.
Some good banter though and the usual amusing sub-plots, generally at Hastings' expense.