"A millionaire strikes a deal on the seedier side of Paris and gives to his heartsick daughter, Ruth Kettering, the "Heart of Fire," one of the world's legendary jewels. Legend has it that the possession of the jewel leads to death - but despite her father's protests, young Ruth decides to take it with her on the Blue Train to the French Riviera, where she has planned a reunion with her former lover. A few days into the journey, Ruth is found dead and her priceless rubies stolen.".
