The Plymouth Express Affair — Agatha Christie

Hercule Poirot is on the case in this early adventure by Agatha Christie. A young woman has been found dead on a train, with robbery of her jewels seen as the primary motive. Her wealthy American father asks the famed Belgian detective to solve the murder. Poirot is in form with Captain Arthur Hastings at his side and supported (hindered?) by the services of Scotland Yard's Detective Chief Inspector Japp as well. This story later became the basis for the Christie novel, The Mystery of the Blue Train.