There is the "Blue train" in a luxurious express, ensuing from London on French Riviera, a tragedy happened. Daughter of the known American millionaire is smothered in an own compartment Ruth Кеттеринг, and all her valuables, including amazing ruby, disappeared. In the same train went to have a rest at the seaside and great detective Эркюль Пуаро, that, certainly, could not remain back from investigation. All round him only and it is said that about the enigmatic kidnapper of valuables on the name of Marquises, and fully sure that this crime - his hands business. However Пуаро obtained information that shortly before that, how an unhappy woman it was found out dead, a husband Ruth, Дерек, went out her compartment.