A hurricane nearly sinks the United World, a ship holding 40 teenagers from all around the world. Most of them flee the ship in lifeboats, however the evacuating children are not counted and five are left behind. The storm blows the battered sailing ship across a reef into the lagoon of an island.
The island, Tambu, ruled by a supposedly 200 year old immortal tyrant called "Q", who came to the island on one of several ships originally bound for New Holland. In the center of the island is a valley in which the descendants of the original ship still live, in the manner of an 18th century colonial community. Adjacent to Tambu is a smaller island, Malo, which is a barren wasteland. It is noteworthy because of a lagoon where prisoners are forced to dive for a "blue weed" which, according to the people of Tambu, is refined into a powder which the Q uses to extend his life.
The children befriend a local family, the Quinns, who help them remain hidden on the island in a swamp avoided by locals because it is, according to local myth, inhabited by the ghosts of the dead. Most of the episode storylines pit the children against the Q, who fears their knowledge of the outside world is a threat to his dominion of Tambu.