The Mystery of the Blue Train

The Mystery of the Blue Train is an Agatha Christie novel first published in 1928, and its detective is Hercule Poirot, who happens to be travelling on the same train as the victim. Ruth Kettering is an American heiress whose marriage is ending, she is on her way to the Riviera to meet the man she loved first, and she is carrying a famous ruby.

The murder is discovered when the train arrives, and the investigation has to establish which of the people around her had both the opportunity and the reason. A husband, a lover, a maid and a stranger all have to be accounted for, and the jewels give the case a market value as well as a motive.

The closed world of a train, a missing stone, a marriage in trouble and a detective who works by talking to everyone are elements Christie used repeatedly in the 1920s and after, and the Riviera setting supplies the moneyed world the victim moved in. The book sits among the early Poirot novels, and its solution depends on timetables and luggage as much as on testimony.