Riding the Blue Train through France on her way to the Riviera, British heiress Katherine Grey (Georgina Rylance) gets pulled into the murder investigation of a wealthy American woman (Jaime Murray). David Suchet reprises his role as famed Belgian inspector Hercule Poirot in this made-for-television adaptation of Agatha Christie's classic mystery novel, co-starring Elliott Gould as the victim's millionaire father.