In the early Victorian period, two young cousins, Richard (Glenn Kohan) and Emmeline Lestrange (Elva Josephson), and a galley cook, Paddy Button (Leo McKern), survive a shipwreck in the South Pacific and reach a lush tropical island. Paddy cares for the children and forbids them by "Law" from going to the other side of the island, as he had found remains from bloody human sacrifices on an altar. He also warns them against eating a deadly scarlet berry.