After spending a bit of a holiday in Paris, Poirot finds himself on a flight to London with an odd assortment of people, some of whom he had met during his stay. When one of the passengers, Madame Gisele, is murdered during the flight by a poisoned dart, Poirot is asked by Inspector Japp of Scotland Yard to assist with the investigation. Gisele was a well-known moneylender with penchant towards blackmail. When Lady Horbury denies knowing the dead woman - which Poirot knows is false - the police clearly have their prime suspect. Poirot however, sees a far more complex plot to gain access to the victims money.