The most ambitious eugenics experiment begins on a deserted Mediterranean island, pitting a British craniologist, Dr Samuel Bates against his French rival, Jean-Louis Belavoix. Two infants, a black boy and a white girl, are raised on the island by a dumb nurse (Norah), away from all human contact but monitored twice yearly by Bates, Belavoix and their assistant, Nicholas Quartley to study their development. Bates claims the white child would show signs of natural superiority, while Belavoix claims the two races would be equal, with each side showing the urge to conquer and ultimately destroy the other. Bates and Belavoix turn into rivals for Norah's attention but she and Quartley are secretly in love, which fuels even more intense competition between the three men. By the time Norah reveals she isn't dumb after all, the experiment is already in jeopardy of collapse. Doubts surface in London over the scientist's real intentions at a time when Darwin's evolution theories begin to emerge. Soon, Captain Perry, responsible for supplying a ferry service to the island, agrees to help Norah and Quartley escape with the children; however, before Perry returns to the island to rescue them, an 'accident' turns their reunion into tragedy.