With several suspects eliminated, Poirot gathers everyone in the saloon, where he reveals the solution – Simon Doyle murdered his wife, with Jacqueline as his accomplice. Poirot reveals that Simon and Jackie were still lovers, and his marriage to Linnet had been cleverly plotted to gain her money. They faked Simon's shooting, leaving him free to murder Linnet while the doctor was being fetched by Ferguson and as Jacqueline was attended to by Miss Bowers. Simon was left alone long enough to run to Linnet's room, shoot her in the head, return to the lounge and shoot himself in the leg through the stole – a third shot of which no one was aware. Jackie covered up. She stole the knife and revolver, then killed the maid and Salome Otterbourne. Simon and Jackie point out that Poirot has no proof, so Poirot convinces Simon that his hands could be tested for grains of gunpowder removed with wax. When they realise that they have been found out, they confess, and in a final love embrace, Jackie covertly takes back her pistol and shoots Simon, then herself.
Later Poirot says goodbye to the remaining guests, reveals that the test was made-up, and Rosalie and Ferguson announce that they are engaged.