One of four low-rent Mexican horror productions from the 1960s which featured an ailing Boris Karloff in supporting roles (and released after his death), this sci-fi/horror quickie features Karloff as a 19th-century scientist who invents a powerful energy device capable of rendering any weapon useless. Although we're led to believe that military forces will soon step in to nab the device, the scientist's laboratory is suddenly invaded by aliens -- who consider the raygun too dangerous to be allowed to fall into human hands. To achieve their ends, the invaders take over the bodies of the scientist and his assistant, who also happens to be responsible for a series of sex-killings in the surrounding village. Several confusing plot twists later, Karloff regains control of his senses and sets the machine to self-destruct before it can fall into evil hands. The filmmakers barely had enough talent to adhere to the simplest of storylines, much less this hodgepodge of cut-rate H.G. Wells posturing and sleazy exploitation.