Captain Hugh C."Bulldog" Drummond (John Howard) and his ever-loving and patient fiancée, Phyllis Clavering (Heather Angel). are about to wed but he becomes involved in a plot to steal an atomic disintegrator with a range of half-a-mile. Madman Rolf Alferson (George Zucco)has control of the weapon but Drummond is suspected of the theft and follows the clues to an island colony.