McCauley and two astronomers are on the Moon on Christmas day, and one of them is stricken with appendicitis.

An eager, space-enthusiast technician (played by Robert Reed of The Brady Bunch) installs a smaller Guidance Control System he designed into the rocket ship. There is now room in the equipment bay for him to stow away on the next flight. But during the 12G takeoff his improvised couch crushes the equipment rack, causing the ship to lose all power before reaching orbit. The uncontrollable ship will quickly re-enter and burn unless repairs can be completed.

McCauley must take four scientists back to the moon to find a deposit of a valuable mineral that one of them stole, so that he can trick the thief into revealing himself.

Tensions mount as final crew selections go forward for a special observation flight of the sun. At the core of the conflict is the potential for one of the crew to be a woman. The other candidates fail to treat her as a highly trained crew person and only see her as a vulnerable woman. Ultimately she uses her gender to solve the problem

A ship tasked with retrieving a malfunctioning Venus probe runs into issues when the scientist in charge, a friend of McCauley's insists on going despite previously disobeying McCauley's orders.

A 3-man team visit the Lunar Observatory, isolated from all Earth signals on the Moon's far side, for routine Radio Telescope work. They pass the time during a long sky-mapping session by taping "A glimpse of lunar life" sound-broadcast. An power fault interrupts and requires a Moon walk to the Radio Telescope. One man is badly injured while returning. Unconscious for days, he responds to the tape-recording and deliriously asks to hear the "sound from the stars." His colleagues comply and make an interesting discovery.

A Soviet Major is the sole survivor of a crash landing near a US advance moon station. Determined to appear blameless, he reports Americans sabotaged the landing and then takes drastic action to destroy all evidence.