Before Professor Gerald Adams (Tom Ricketts) dies he tells his daughter Bonnie (Lucile Browne) of his discovery of a radium deposit located on an island off the African coast. Ben Arnold (Walter Miller and his girlfriend, Aileen Chandos (Beulah Hutton) , decide to get the mine for themselves by befriending Bonnie. Sea Captain Harry Drake (Kenneth Harlan) falls in love with Bonnie and vainly tries to help her see through their facade, but he himself is discredited in the eyes of Bonnie by the scheming pair and Ben's henchman "Bull' Black (William L. Thorne'. Later, after Ben threatens her life, Aileen deserts him and joins Harry, Bonnie and ship's mate "Briney" (Andy Devine) and they, aided by Cebu (Everett Brown (I)') , are engaged in a fight to the finish against Ben, Black and their henchmen.
