This Island Earth

A team of top nuclear scientists is assembled by the mysterious Exeter at a high-tech laboratory in Georgia. His mission, kept secret even from the researchers, is to develop new sources of atomic energy, which are needed to defend his home planet, Metaluna, from its interplanetary rival, Zagon. When two of the recruits begin to suspect Exeter's true identity and motive, they attempt to escape. But before the runaways can reach safety, the aliens intervene and carry them off in a last-ditch effort to save Metaluna. (official distributor synopsis)