Ann Burton and Jack Baker are en route to Cape St Roque in South America in the stolen stratosphere ship with the two diamond smugglers Vic and Joe, when they sight a castaway on a small island off the coast, near the equator. Sighting the airplane, the castaway evidently faints and falls near to the fire he has built to attract the attention of a rescue ship. But in attempting to land the huge ship on the small island, Jack finds that the landing gear is firmly stuck...