A murder is committed on a Nile steamer, but Hercule Poirot is on board... Almost everyone on the S.S.Karnak, cruising the Nile, has a reason to want heiress Linnet Ridgeway dead. Her jewels are coveted by elderly Mrs. van Schuyler, her maid is upset because Linnet won't give her a promised dowry, writer Salome Otterbourne is facing a libel suit brought by Linnet, Salome's daughter Rosalie wants to protect her mother, American Andrew Pennington has been embezzling from the Ridgeway family, and former friend Jacqueline de Bellefort is upset that Linnet stole her fiance, Simon, away from her. Belgian sleuth Hercule Poirot must unravel the mystery when Linnet (and some of the others) turn up dead.