The Theft of the Royal Ruby (S03E09)

Poirot intends to enjoy a serene Christmas alone with a box of chocolates, but his plans are abruptly interrupted when the British government seeks his immediate assistance. The young Prince Farouk, part of the Egyptian royal family visiting London, has misplaced a renowned ruby, and the situation is considered crucial for national security. Poirot must set aside his holiday to unravel the mystery surrounding the missing gem.