"You're looking at a species of flimsy little two-legged animals with extremely small heads whose name is Man. Warren Marcusson, aged thirty-five. Samuel A. Conrad, aged thirty-one. They're taking a highway into space, Man unshackling himself and sending his tiny, groping fingers up into the unknown. Their destination is Mars, and in just a moment we'll land there with them." - Rod Serling, opening narration.

Two men embark on a voyage to Mars; one, a pessimistic and fearful scientist who would rather remain behind, the other an idealistic astronaut who believes that people will be the same regardless of where in the universe they are found. Upon landing on Mars quite severely, the more optimistic of the two men is killed, leaving the scientist to venture alone onto the great Red Planet.

"Species of animal brought back alive. Interesting similarity in physical characteristics to human beings in head, trunk, arms, legs, hands, feet. Very tiny undeveloped brain; comes from primitive planet named Earth. Calls himself Samuel Conrad. And he will remain here in his cage with the running water and the electricity and the central heat as long as he lives. Samuel Conrad has found the Twilight Zone." - Rod Serling, closing narration.