An American astronaut mysteriously disappears from his spacecraft as it parachutes to Earth. He is apparently replaced by or turned into a large, radioactive, humanoid monster. A team of scientists and military men attempt to capture the monster.

Directed by: Bill Rebane & Herschell Gordon Lewis
Written by: Bill Rebane & Jeff Smith & Dok Stanford
Runtime: 70 minutes
Tagline: An astronaut went up- a "guess-what" came down!
Cast:
Henry Hite Henry Hite
Frank Douglas as a Monster 
Phil Morton Phil Morton
Col. Steve Connors 
Lois Brooks Lois Brooks
Dr. Nora Kramer (unconfirmed) 
Rork Stevens Rork Stevens
 
Robert Simons Robert Simons
 
Peter M. Thompson Peter M. Thompson
Dr. Chris Manning