Three men have just begun a record breaking five month stay aboard the space station Threshold I. Mere hours into the mission, disaster strikes. With Sector C leaking air, the mission must be aborted. The shuttle, now separated from the damaged space lab, plunges into the freezing waters of the Arctic. Astronaut Ed Tyler is the first to exit the shuttle, and the last. The shuttle explodes hurling Tyler across the Arctic wasteland.

An alien race, the Deiei, hidden deep within the Arctic ice, have been monitoring the situation. They decide to remove the unconscious astronaut from the Arctic surface, in order to avoid possible detection when a rescue party arrives.

When Ed Tyler awakens, he finds himself on trial. The Deiei will determine his fate. They decide to keep him alive and under observation within the underground complex. He will remain a prisoner forever.

Tyler soon learns that the Deiei had a hand in the evolution of the human race. They have been monitoring their progress for countless centuries. Ashamed at what the human race has become, they are determined to eradicate mankind and start anew.

Confident that he can do no harm, the Deiei leave Tyler's quarters unguarded. He proceeds to take one of the alien space suits and arms himself with atomic transistors. With this power, he is able to escape the alien complex.

Hours later, the city of Reykjavik, capital of the island nation of Iceland, is under attack. The Deiei have bombarded the city with nuclear particles causing the earth to collapse. Tyler once again confronts the Deiei, this time with disastrous results. An atomic explosion destroys the Arctic complex reducing it to rubble. Tyler quickly returns to Reykjavik to aid it's citizens and repair the damage done by the alien attack.

Unbeknownst to Tyler, a group of the Deiei has survived. After seeking out and destroying Tyler, they intend to abort their experiment and destroy the planet Earth.