A technological civilization of humans finds a remote island inhabited by intelligent humanoid salamander creatures. They take three of them captive and bring them home to their big city to conduct experiments on them. The experiments go awry and the salamander creatures grow into huge monsters. They wreak havoc in the city while the armed forces of humans try to stop them. One of the salamander creatures manages to escape and swim back to his island, where the rays of the sun turn him back into his original form.