Hercule Poirot is asked by American millionaire Rufus Van Aldin to investigate the murder of his daughter, Ruth Kettering, killed on The Blue Train on the way to Nice with her priceless collection of rubies. This is a Hastings-free inquiry, so interestingly the brilliant detective enlists the help of two young women, recent heiress Katherine Grey and her cousin Lenox Tamplin, who do actually help him with pieces of the puzzle. Not only does M. Poirot work with these would-be junior sleuths, he demonstrates a terrible temper when questioning one suspect, actually shaking his fist and yelling at him. And the book is notable for the first mention of St. Mary Meade, later Miss Marple’s hometown. Beware the maids and clerks—they are not to be trusted in the 1920s!