Eight people at a remote Scottish inn find themselves confronted by a woman from Mars, who has landed her flying saucer for repairs but intends to soon conquer the Earth and enslave its men for breeding purposes.
An American travels to East Africa, where he tries to find out how his brother died.
Several murders of nuclear scientists, that baffles Scotland Yard, occur in London about the same time that Bill Locklin, a special officer from the United States State Department, arrives to oversee the transfer of Professor Leon Dushenko, a Russian scientist who as fled the U.S.S.R. An attempt is made on Dushenko's life with a monkey's paw-print found at the scene.
