While on holiday in Egypt, Poirot is drawn into a fued between two former friends.
Newly engaged and madly in love couple Jacqueline de Bellefort and Simon Doyle have fallen on hard times. In order to afford getting married, and moreover pay for their planned honeymoon in Egypt, Jacqueline introduces Simon, who has just lost his job in the city, to her old school-friend Linnet Ridgeway in hope that Linnet might help to get him a job. Within weeks of the introduction, Linnet, a rich and achingly beautiful American heiress, has however seduced Simon and married him herself. On Simon and Linnet's honeymoon cruise down the Nile three months later, Jacqueline appears seeking revenge. The next morning Linnet is found dead - shot through the head in her sleep. Jacqueline naturally becomes the head suspect in the case, but she turns out to have a water-tight alibi for the time of the murder. Belgian detective Hercule Poirot, who is also a passenger aboard the cruise, is about to uncover a murder so carefully planned that even he must admit that the murderer has thought of everything. That is, everything except one thing: Hercule Poirot.
When Linnet Doyle, the richest woman in London, steals and marries her best friend's fiancé, the best friend gets her revenge by hounding the newlyweds throughout their honeymoon.