The Theft of the Royal Ruby

Poirot prepares to spend a quiet Christmas on his own with a box of chocolates, but he has to give up his plans when the British government asks for his urgent help. Prince Farouk, a young member of the Egyptian royal family visiting London, has lost a famous ruby, and this is deemed to be a matter of national security. The Prince unwisely lent his jewel to a strange young lady who promptly vanished with it, and Poirot forms a complicated plan to catch the thieves, harnessing misdirected romantic urges.