The millionaire heiress, Lynette, was found shot in the head aboard her honeymoon yacht, her prized £50,000 pearl necklace missing—a clear indication of a premeditated murder for financial gain. As Poirot searched for clues, Lynette's maid, Louise Bourget, was also found murdered in the room, clutching a torn corner of a 1,000-franc note, suggesting she had uncovered the killer and attempted blackmail, only to meet her demise.

Fortunately, Mrs. Otterbourne was the sole eyewitness to the murder. However, just as she was about to reveal the identity of the murderer, she was shot dead by a bullet from outside the window. In the end, Detective Poirot unraveled the intricate web of clues, including seemingly insignificant details like the consumption of drugged wine on the night of the murder, a shawl with bullet holes found in the Nile, a nail polish bottle stained with red ink on Lynette's vanity, and the capital letter "J" written on the wall in blood.

Carefully piecing together these seemingly unrelated and convoluted clues, Poirot deduced that it was Jacqueline and Simon who conspired to murder Lynette. This unexpected twist leaves readers astonished at the unraveling of the mystery. As with many detective novels, the story concludes with the true culprits, Jacqueline and Simon, taking their own lives.