While traveling from London to Kingfisher Hill to discretely investigate murder allegations against a wealthy client's wife, Hercule Poirot swaps seats with a nervous train passenger before a second killing is complicated by a series of impossible confessions.

In 1794 Stockholm, Jean Mickel Cardell, the one-armed watchman, investigates the death of Eric Three Roses' beautiful wife on their wedding night at the behest of the girl's mother, who is desperate for justice.