McCauley is on the Moon conducting geographical operations with Lou Marlowe and Mel Rumbough. Captain Webb calls from the moonbase to inform them that an unidentified object is approaching on radar. McCauley tells Webb to inform him if anything changes and goes back to work.
The approaching Russian spaceship is the NK1. The commander, Major Kralenko, tells his men to prepare for landing. The pilot refuses, pointing out that they've gone off course, and tries to relieve Kralenko of command. Kralenko ignores him despite the warning that the course recorder will show the change in flight plan, and plots a landing pattern.
When the NK1 comes down, Webb informs McCauley. They're 200 miles from the Russian moonbase and have no idea what the Russians are doing. McCauley and his men see an explosion and the colonel tells Webb that they have an incident on their hands.
Kralenko wakes up and discovers that he's the sole survivor of the crash. He calls Colonel Alexandrov at the Russian moonbase and tells him that the Americans sabotaged the flight by jamming its landing radar. Since Kralenko only has two hours of oxygen, Alexandrov tells him to recover the course recorder and go to the American moonbase, an hour away. Kralenko seemingly agrees and signs off, and then tries and fails to remove the course recorder.
The major gets clear of his ship just in time as McCauley and his men. While Kralenko watches from hiding, McCauley enters the NK1 and confirms that two of the men dead. Assuming that is the entire crew, McCauley calls Webb and tells him that there were no survivors. As they head back to base, Webb tells them that Alexandrov has informed them that he heard from Kralenko so at least one man survived the crash.
At Earth Control, Major General Mallon meets with a Russian general, who demands the course recorder. Mallon suggests that they send a joint team to investigate the crash, and the Russian general agree. However, he insists that the Americans stay away from the NK1 until then. Once they agree, the Russian general starts to leave but then asks Mallon if he trusts McCauley. Mallon assures him that McCauley is a man of unquestionable integrity. However, the Russian warns him that someone's integrity will be questioned. Mallon then calls McCauley and tells him what the situation is, and that they're to find Kralenko and bring him safely to the moonbase.
Kralenko goes back into the wreck but fails to remove the course recorder that would prove his negligence. He then goes outside and waits until McCauley and the others return. When McCauley goes back inside, he realizes that someone tried to pry out the course recorder. He also discovers that the missing man took the extra oxygen tanks from the two dead men. He goes outside and begins searching the area with Rumbough and Marlowe, and tells web to notify him if Kralenko arrives at the moonbase.
The major goes to the moonbase and enters through the airlock, and then draws a gun on Webb to stop him from using the radio. When Webb tries to warn McCauley, Kralenko shoots him. When McCauley calls in, Kralenko tells him that he is in charge of the moonbase. To stop McCauley from coming inside, Kralenko informs the colonel that he has put the badly injured Webb in the airlock. If they open the door then Webb will asphyxiate.
When McCauley and his team arrive at the moonbase, McCauley tells Kralenko that both of their superiors know that Kralenko escaped on foot. The major says that he plans to frame McCauley and Webb for sabotaging his ship, and claim that he shot them when they tried to destroy the evidence. Kralenko will take some explosives to the NK1 and blow it up, erasing the evidence against him.
McCauley takes the others behind a rock, blocking radio transmissions. Once they can't be overheard, the men discuss their options. The nearest cache is too far away to get there and refill their oxygen tanks before they run out of air. McCauley decided to trick Kralenko into confessing. All three men turn on their suit recorders and then step back into line-of-sight of the base. Once McCauley gets Kralenko to admit his plan, the colonel reveals that he recorded the entire conversation. The major offers them oxygen if they'll leave the tape recorders behind, but McCauley refuses and says that they're heading to the Russian moonbase.
Once McCauley leads his men out of sight, Kralenko dons a suit and goes after them to get the recorders. McCauley and the others have actually hidden a short distance away, with only two minutes of oxygen remaining. When Kralenko walks by them, they subdue him and take him back to the moonbase. They discover that Webb has died of his wound and McCauley calls Mallon at Earth Control to tell him that they have the guilty party and his taped confession.
Later, McCauley returns to Earth and meets with Mallon and the Russian general. The general admits that Kralenko's personality file showed that the major couldn't tolerate failure and was driven to succeed at all costs. Ironically, the Russian review board discovers that the crash was due to mechanical failure, not Kralenko's incompetence. The general thanks McCauley for how he handled the matter and they all agree that it was a good thing they found out the truth before the situation escalated into war.