In a relatively energy-poor future, engineers have built a satellite that captures sunlight and transforms it into petawatts of microwave energy which is beamed down to the planet and turned into electrical energy. To lower costs, the satellite has been designed to be autonomous, repaired and maintained by a horde of robots.When the station slides off-beam, its enormous potential as a weapon is quickly realized.

Chief Operating Engineer Graciella Ch'ou, Chinese-American daughter of the man who built the station, General Ethan Rigsby, is the only person with the knowledge and skills to fix the problem. But to do so, she must battle not only her own father, but as well a US Army space combat mission tasking to destroy the station, a group of mercenaries determined to capture it for their own purposes, and the station itself, which can use it horde of robots as a means of self-defense. Graciella's most implacable enemy, however, is space itself, where the slightest mistake spells death. Racing against time and implacable foes, Graciella must shut down the station before it triggers a dies irae – a day of wrath from heaven, an apocalypse which might destroy all life on earth.