The light ship Altares and her crew plummet through the maw of a powerful black hole and emerge in a strange new universe. Running low on fuel and in need of repairs, Captain Harry Masters pilots the spaceship into orbit around an Earth-like planet. But before the crew can make planetfall, they must first attempt a dangerous manoeuvre to reach the towering gas clouds at the limit of the star system in order to refuel.

Soon, the crew of Altares find themselves trapped between the malevolent alien force roused from slumber beneath the city and preparing for war in orbit, and a dangerous enemy from the Earth itself bent on seizing control of the light ship so far away from home...

A sequel to the classic Gerry Anderson made-for-TV movie.