When the people of Bellania II witness a triple eclipse of their sun, Bel -- an impossibility, as they only have one moon -- it is the beginning of the end for an entire solar system. Their sun is shrouded in night for a month -- then returns to them a younger, brighter, hotter star. But how?100,000 years later, the Doctor and Sam arrive on Belannia IV, where 20,000 people are under threat as a catastrophe threatens -- immense gravitational and dimensional disturbances are rioting through their sector of space. Sam is swept away by desperate crowds trying to get off their world, and becomes involved in daring rescue attempts. The Doctor tries to stabilize the local gravity fields and help halt the devastation, but the TARDIS is lost to him.Meanwhile, a religious suicide-cult leader attempts to destroy himself on the deadly heated surface of Belannia II, but he does not die. He returns stronger, and with a new religion he is determined to spread through Bel's system. His word may prove more dangerous even then the terrible forces brought into being from Bel's sun. Just what has happened to the star Bel -- and will the Doctor hive time to do anything about it?