This is the second of three films in producer Ivan Tors' "OSI" series. The scientists are taken to the "Snake Mountain Proving Grounds, operated by the Office of Scientific Investigation," according to Dr. Dryden. Dr. Stanton's desk nameplate indicates he is "Chief of Investigations."

Cinematographer Stanley Cortez was fired and replaced (by Joseph F. Biroc) after clashing with director Herbert L. Strock, but still retained screen credit.

Actually, when the scientists arrive, they are told that the base is operated by OSI. Also, the jeeps seen at the beginning have OSI stenciled on the hoods.

The film features actors who appeared in Ivan Tors' other "OSI" films, Gog and The Magnetic Monster. These included Richard Carlson, King Donovan, Herbert Marshall and Michael Fox; however the actors played different characters in each film.

Photographed in color by Color Corporation Of America. Many TV prints are in black & white.

Richard Carlson's directorial debut.