"The luxurious Blue Train carries its passengers across France, from dreary wintertime England to the sunny French Riviera. When it arrives at Nice, a guard attempts to wake serene Ruth Kettering from her slumber. But she will never wake again -- she has been killed, and a heavy blow has disfigured her features almost beyond recognition. What is more, her precious rubies are missing and her ever-present maid was dismissed from the train back in Paris....