Richard (LEONARDO DiCAPRIO) is a young American traveler who's arrived in Thailand looking for adventure beyond the typical tourist trappings. While he's immediately drawn to an alluring French woman, Francoise (VIRGINIE LEDOYEN), who's staying next door with her boyfriend, Etienne (GUILLAUME CANET), Richard gets his opportunity upon meeting Daffy (ROBERT CARLYLE).
He's an older and quite delusional man who rambles on about a secret island, a paradise with a perfect beach that few have ever seen. Richard doesn't think much of this, attributing the story to the pot they smoked, but the next morning he discovers that Daffy left him a map to that island.
Quickly convincing Francoise and Etienne to join him, the three head off for the remote island, but not before Richard shares the story about it - as well as a copy of his map - with some stoner tourists who are intrigued by rumors of it being overgrown in pot.
Eventually making it to the island after a long swim in potentially shark-infested waters, the three discover to their horror that part of the island is run by armed drug farmers. Managing to avoid detection, Richard and his friends head off to the other half where they're met by Keaty (PATERSON JOSEPH), a fellow traveler who leads them back to a community of other travelers, loosely ruled by Sal (TILDA SWINTON) and her handyman boyfriend, Bugs (LARS ARENTZ HANSEN).
While everything seems quite wonderful and the three frolic on the beach and in the jungle with their new friends, unrestrained passion, eventual dissention and the possibility of those with Richard's copied map arriving on the island soon threaten to destroy their idyllic paradise.