Led by the intrepid Col. Floyd Graham (Lloyd Bridges), a crew of astronauts (Osa Massen, John Emery, Noah Beery Jr. and Hugh O'Brian) embarks on the first manned mission to the moon. But as often happens in early-1950s sci-fi adventures, their mission goes awry, and they crash-land on Mars. Instead of a barren rock, however, the crew finds a war-ravaged world inhabited by hostile cavemen and radiation-riddled creatures.