Brilliant Belgian detective Hercule Poirot (David Suchet) unravels another Gordian knot of a mystery when a woman implores him to find the real guilty party responsible for murdering her father 14 years earlier. Lucy Crale's (Aimee Mullins) mother was executed for poisoning her husband, but Lucy now believes that someone else may have committed the crime. Poirot agrees to interview the five people who were present at the time the murder was committed.