Death On The Nile By Agatha Christie

The story follows the main character, Hercule Poirot, where he embarks on a vacation in Egypt, but finds himself solving two murder cases. Hercule Poirot is a French private investigator that is famous for solving some of the world's most perplexing mysteries. While he is on vacation and sailing on a river boat up the Nile, he finds himself in the middle of not one, but actually two murder mysteries.

It all starts when Linnet Ridgeway, one of the richest young ladies in London, steals the fiancé of her best friend, Jacqueline de Bellefort. Linnet Ridgeway not only steals Simon Doyle away from her friend Jackie, but she marries Simon and they head off on their honeymoon to Egypt. In revenge for stealing her man, Jackie starts showing up at all the locations where the newlyweds are present and harasses them. Coincidentally, Hercule Poirot is vacationing in Egypt and boards the same ship to sail up the Nile that the Doyles and Jackie de Bellefort take.