It is the spring of 1923 and the Honorable Daisy Dalrymple is on her way to a stately home in Scotland to research her next article for Town and Country. On board the Flying Scotsman, the famous London-to-Edinburgh train, Daisy meets an old schoolfellow, Anne Bretton. Anne, along with all of her relatives, is en route to visit the deathbed of the family scion and notorious miser, Alistair McGowan. As it currently stands, Alistair's will leaves the entire family fortune to his brother Albert, and the rest of the family is rushing to his side, each hoping to convince him to change his will in their favor.
Daisy, meanwhile, has her hands full taking care of Detective Inspector Alec Fletcher's young daughter Belinda, who ran away from home and stowed away aboard the train. She barely has time to take notice of the intricate family feud taking place all around her—that is, until Albert McGowan is found murdered on the train and Daisy is surrounded by an entire family of suspects.