NASA Mission Control on Earth monitor the launch of the first manned spaceflight Arrow One. At first, everything goes smoothly. However, Arrow One and its eight-man crew soon disappears off of radar after a short period of solar interference.
After Arrow One crashed, commanding officer Robert G. Donlin makes his first entry. He notes that they've landed on an uncharted asteroid, cause unknown. The asteroid is a barren wasteland. Four of the crew are dead, and the survivors are Donlin, Flight Officers Corey and Pierson, and Navigator Jim Hudak, who is seriously hurt. The radio is gone and the bulk of supplies were destroyed in the crash. Corey angrily snatches away the notebook and says that they have to focus on survival. Donlin reminds him that they're he's still in command takes his notebook back. Pierson sides with Donlin and Corey reluctantly sits down.
As Donlin gives water to Hudak, Pierson admits that he doesn't know what happened to Corey during the crash. Corey objects to them wasting water on an injured man, pointing out that Hudak won't live through the afternoon. Donlin says that they'll help him no matter what, and assigns shifts to digging graves for the four crewmen. Pierson takes first shift and points out that the of the Sun isn't any different than it is on Earth. He points it out to Donlin, who agrees. They figure that the asteroid shares an orbit with Earth, and Donlin notes that Arrow One is a prototype so there won't be another ship coming. As he checks the supplies, Corey finishes off his canteen.
Later, Donlin and Corey go scouting and find nothing. They come back and tell Pierson what little they've found, and Donlin gives Hudak some more water. Corey objects, telling Donlin not to give the dying man his water, and the two men fight. The canteen gets knocked over and while they fight, Pierson confirms that Hudak has died. Corey tries to take Hudak's canteen, and Pierson stops him and warns that if he catches him stealing again then he'll kill him. Donlin orders Pierson to back off and says that after sunset, they'll start moving out in all directions and look for anything that can keep them alive.
After sunset, Donlin stands watch while the other two begin scouting. Corey returns and reports that he found nothing within 15 miles. He says that Pierson went south while he went west, despite Donlin's orders to stay together. Donlin points out that he started out six hours ago with a half canteen, and now its three-quarters full. Corey says that he found Pierson dead at the foot of the mountain, and Donlin says that he's going to bring Pierson's body back. When the flight navigator says that he can't make it, Donlin takes his gun and says that he wants to see the corpse for himself.
Corey leads the way to Pierson's body and finally says that he needs to rest. He starts to pick up a rock but Donlin orders him to move out. They finally come to the spot only to discover Pierson is gone. Corey spots tracks showing that Pierson crawled away, and Donlin figures that Corey abandoned him without checking. Disgusted, Donlin calls for Pierson and follows the tracks.
The two men finally locate Pierson, lying in a ravine. The man is dying, and tries to gasp something out to Donlin. He gestures to the top of the mountain, but can't talk. He finally draws a shape in the dirt: two perpendicular lines, one longer than the other. Pierson dies and Donlin figures that he was trying to tell them something. As he starts climbing, Corey grabs his gun and Donlin figures that Corey killed Pierson. Corey guns him down and checks the body, and discovers that he hit the colonel's canteen. Taking the gun, Corey sets out.
Corey climbs up the mountain, scrabbling for handholds and using the last of his water. He finally reaches the top and screams at Pierson, and then breaks into hysterical laughter. Corey realizes what Pierson was trying to describe and stares at the telephone poles... and the highway down below. A sign shows that he's 97 miles away from Reno, and Corey realizes that they never left the earth.