Loading... Please wait...An expedition to the planet Krop Tor, a planetoid in orbit around a Black Hole, goes terribly wrong. The Black Holes gravity field should in theory crush the planet to pieces but a mysterious energy force deep within the planet is keeping it in place. The humans and their slave race the Ood set up a temporary Sanctuary Base on the planets surface to study and mine down to the power source. When the power source is finally removed the escaping humans in their Rocket ship are unable to escape the pull of the Black Hole, until finally pulled free by the Doctor in his TARDIS.