On the Blue Train is Kristel Thornell’s reimagining of Agatha Christie’s mysterious disappearance in 1926. Thornell might have let her imagination fly, given that both Dorothy L. Sayers and Arthur Conan Doyle involved themselves in the nationwide search for the missing woman, but instead she has stuck close to the established facts: Agatha was grieving over her beloved mother’s recent death when her husband Archibald asked for a divorce; there was a fracas; Agatha’s car was found abandoned; she vanished and was discovered ten days later, using the surname of Archibald’s lover, at a spa hotel in Harrogate.