Hercule Poirot takes a quiet holiday at the Jolly Roger Hotel, an exclusive resort on Smugglers' Island off the Devon coast, reachable from the mainland only by a causeway that floods at high tide. Among the guests is Arlena Marshall, a celebrated former actress whose beauty draws every eye and whose conduct unsettles the small, gossiping party of holidaymakers. Her devoted husband endures the whispers in silence, her resentful young stepdaughter withdraws, and a married guest grows openly infatuated with her, straining tempers across the sun-baked beaches and coves. Poirot, watching the shifting alliances and jealousies, senses that the idle pleasures of the resort conceal something far darker, and remarks that evil exists everywhere, even here under the sun. When a body is discovered in a secluded cove, the holiday turns into a murder inquiry, and the tide of suspicion sweeps across nearly everyone on the island. Alibis appear airtight, witnesses contradict one another, and the timing of every movement on the beach becomes crucial. Poirot must sift the trivial from the significant, testing each account against the rhythm of the sea and the habits of the guests. As he reconstructs the hours surrounding the killing, small observations that seemed meaningless take on weight, and a pattern emerges from the apparent confusion. The case turns less on physical clues than on human nature, on the difference between how people present themselves and what they truly want.