On a luxurious cruise on the Nile River, a wealthy heiress, Linnet Ridgeway (Lois Chiles), is murdered. Fortunately, among the passengers are famed Belgian detective Hercule Poirot (Peter Ustinov) and his trusted companion, Colonel Race (David Niven), who immediately begin their investigation. But just as Poirot identifies a motley collection of would-be murderers, several of the suspects also meet their demise, which only deepens the mystery of the killer's identity.