The desire to find something real - to connect with something or someone - is what drives Richard (Leonardo DiCaprio), a young American backpacker who arrives in Thailand with adventure on his mind. Travel, he asserts, is the search for experience, the quest for something different.

At a cheap hotel in Bangkok, Richard meets a French couple, Etienne (Guillaume Canet) and Francoise (Virginie Ledoyen). He also encounters Daffy (Robert Carlyle), an older traveler ravaged by years of sun and drugs. Rambling and paranoid, Daffy tells Richard the improbable tale of a secret island, a paradise on earth: the perfect beach, unsullied by tourists.

The next day, Richard finds a piece of paper pinned to his door. It is a hand-drawn map of the island described by Daffy. This, Richard realizes, may be the "something different" he has been looking for. He goes to find Daffy only to discover his corpse, the crazed man's wrists slit by his own hand.

Richard persuades Francoise and Etienne to join him and they set off on a journey, following Daffy's map. To get to "the beach" they must risk their lives by swimming across an open sea from one island to another, crawling past armed guards and jumping from the top of a 120-foot waterfall. Reaching their destination, they find a small community of travelers like themselves, living in secret. They are welcomed into the group, and the island paradise becomes their home, sapping them of all will to return to the world they knew before.

Yet beneath the surface, this heaven on earth is less than perfect. Personal conflict and petty jealousy ferment to create a violent rivalry, and a series of tragic events fragments the community. Increasingly isolated and disturbed, Richard finds himself more than witness to an incident of blood-shed. The dream has become a nightmare; paradise has turned to hell. Now his only goal is to leave. But escape will not be easy, for the beach is a secret place, a secret that some will defend to the death.