William Blood, an extraordinarily healthy Englishman, makes his living as a human guinea pig for medical research. He loses his job, however, when his physical fitness prevents him from catching a common cold after spending the night in a meadow. Almost immediately he is recruited by Professor Davidson of the Atomic Research Center, who plans to make Blood the first man on the moon, a project that is concealed from him. When Blood emerges from tests in refrigerators, in hot boxes, on rocket sleds, and in centrifugal whirlers, Blood arouses the envy of Leo, an astronaut who had hoped to win the prize money offered to the first man to attempt a landing on the moon. This situation is remedied, however, when the scientists brainwash Leo into loving his rival. Although Blood eventually learns of the fate awaiting him, the prize money is too tempting, and he agrees to undertake the flight. His spaceship is launched from an Australian range; and the scientists are able to contact him. Unfortunately, he lands in the middle of the Australian bush country rather than on the moon. Blood then heads back to England and his Soho stripper girl friend, Sally.