When the sailing ship United World is almost sunk by a hurricane, the forty teenagers who are sailing in her scramble for the lifeboats, but five are overlooked in the general panic. Along with the ship, they are driven into the lagoon of a mysterious island, Tambu. Here, they find a lost civilisation: the descendants of settlers originally headed for New Holland, who still live an eighteenth-century lifestyle. But they are under the domination of the mysterious Q, a seemingly immortal being who allegedly prolongs his life with the aid of a blue weed obtained from a nearby island, Malo. The five children, with the assistance of the Quinns, a local family, seek to avoid the malevolence of Q, who fears they are a threat to his domination of the island.
The Lost Islands was another production from New Zealand-born Roger Mirams, who was also responsible for such Australian television programs as The Terrific Adventures of the Terrible Ten, The Magic Boomerang, The Adventures of the Seaspray, and Spyforce.