Commander Kit Draper (Paul Mantee) is an astronaut who co-pilots a landing craft with Col. McReady (Adam West). They have to pilot this craft and land on the planet Mars due to a failure of equipment on their rocket ship. McReady does not last long. Draper must try to figure out how to go on living on the alien planet. He runs into a loyal monkey, Mona (Barney), is cautious with his oxygen supply, and finds things to eat and drink and a cave to live in. For months, he can still hear the mother ship orbiting the planet and carrying supplies. He finally meets another being whom he calls Friday (Victor Lundin), who had been enslaved for years by aliens. They both must outwit Friday’s former captors.