Almost everyone on the S.S. Karnak, cruising the Nile, has a reason to want spoiled, selfish and beautiful heiress Linnet Ridgeway Doyle (Lois Chiles) dead. Her jewels are coveted by elderly Mrs. Van Schuyler (Bette Davis); her maid, Louise, is upset because Linnet won't give her a promised dowry; writer Salome Otterbourne (Angela Lansbury) is facing a libel suit brought by Linnet; Salome's daughter Rosalie Otterbourne (Olivia Hussey) wants to protect her mother; Andrew Pennington (George Kennedy) has been embezzling from the Ridgeway family; and former friend Jacqueline De Bellefort (Mia Farrow) is more than a little angry and upset that Linnet stole her fiancé, Simon Doyle (Simon MacCorkindale). Renowned Belgian sleuth Hercule Poirot (Peter Ustinov) must unravel the mystery when Linnet (and some others) turn up dead.—Ron Kerrigan