In a palace in Ramat, a prince entrusts a package of jewels to his pilot, in the hope that he can smuggle them to England. The pilot, in turn, hides them in his sister's baggage. But before the packet reaches its destination the prince and the pilot are both dead. Then Joan, the pilot's sister, travels to England with her daughter Jennifer where she will be attending boarding school. Soon they find out that an unsuspecting student has become a magnet for evil and death and that a killer is terrorizing the famous school for girls. Somehow the two cases are linked and only Poirot can solve this double mystery.