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 maneuver to reach the towering gas clouds at the limit of the star system in order to refuel. In the plumes, the crew encounters the first of many mysteries - a silent alien colossus with clues that point back to the blue world. On the planet's surface, navigator Tom Bowen, Jane Masters, and David Bowen discover the remains of a city and proof of visitations by more than one advanced race, while aboard the light ship Doctor Anna Bowen experiences a ghostly reunion with a face from the past. 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.