Shortly after arriving on Earth in the 51st century, The Doctor and Izzy are greeted by Marquez, the android servant of Crivello, an aged scientist only kept alive by his complete immersion in a nutrient tank. Crivello is attempting to create an artificial sun for a new solar system for humanity after Earth is engulfed by solar flares. The Doctor discovers the sun is alive. Having built a rapport with the artificial sun, The Doctor orders it to travel to an unpopulated arm of the Crab Nebula to become humanity's new home.