Publisher's Synopsis
In the far future, the inhabitants of Tarsus Six face a desperate struggle to evacuate their world before their sun, Tarsus Ultra, collapses into a cataclysmic spatial anomaly. When the Doctor navigates the TARDIS to a space station orbiting Tarsus Six, his companion Ace assumes that he intends to offer their assistance. But it becomes clear that the Doctor has an agenda of his own.