The TARDIS brings the Doctor and Rose to Sanctuary Base Six, a research facility on a planet which -- against all the laws of physics -- orbits a black hole. Meeting the crew, the Doctor is astonished to find that they have unearthed writing so ancient that even the TARDIS can't translate it. The goal of the expedition is to drill miles below the planet's surface and locate the incredible power source which is counteracting the black hole's massive gravitational pull. But Toby Zed, the team archaeologist, is being haunted by a malevolent voice. The telepathic Ood servants are behaving very strangely. And the Beast has awakened...