In the future Earth, the Zeus 4 rocket is launched into space. It maintains communications with the South Pole station, run by General Cutler.
The TARDIS lands near to the arctic base. The Doctor, Ben and Polly venture out into a snowstorm. They are spotted by the crew of the arctic base, who bring them inside. General Cutler wants them confined until he has time to deal with them.
Suddenly, the crew find that the Zeus rocket is more than 100 miles off course. The astronauts on the spacecraft try to confirm their location from Mars but instead site another planet. They also find that they are losing power.
The Doctor demands to see Cutler. He hands him a note predicting what he is about to see. Cutler and his men give course correction to bring the Zeus 4 back. The spacecraft starts tumbling out of control. The increasingly exhausted crew are able to bring it under control but they struggle to bring the craft safely back to Earth.
The Doctor points out that the new planet has identical continents to the Earth. Barclay opens the Doctor's note and finds that it predicted what they would see. The Doctor tries to explain the nature of the planet, but Cutler won't listen. The Doctor tells Ben and Polly that they will soon have visitors from the tenth planet.
Cutler is suspicious and sends men out to break into the Doctor's "hut". As they emerge, a spacecraft lands nearby. Metal creatures appear and attack the men, killing all three…