The TARDIS lands on a sanctuary base used for deep space explorations. The Doctor (David Tennant) and Rose (Billie Piper) discover strange writing which the TARDIS cannot translate. The Doctor believes it must be extremely old. They meet the Ood, a peaceful race of empathic slaves who work there and communicate with a glowing sphere they place against their foreheads. The time-travellers meet the research crew: Zach (Shaun Parkes), Ida (Claire Rushbrook), Jefferson (Danny Web), Scooti (MyAnna Buring), and Toby (Will Thorp). They are exploring the mysterious Krop Tor, a planet somehow orbiting a black hole.

Captain Zach explains that a gravity funnel surrounds the planet, so they can enter and leave the vicinity of the black hole. There is a huge energy source ten miles below the planet’s surface, which they are drilling to reach. The base experiences an earthquake and part of the base falls into the planet, taking the TARDIS with it. Rose and the Doctor are stranded, so they begin to help the crew.

As the drill nears its target, they sense a malevolent presence. The Oods’ translation spheres play messages of the Beast awakening, and Toby is possessed. Toby kills Scooti when she sees him outside the base with no spacesuit. Finally, the drilling is ended, and the Doctor descends the drill shaft with Ida. Deep in the planet, they find a large circular disc with indecipherable markings. It begins to open. The Beast repossesses Toby and enters all the Ood, who now call themselves the Legion of the Beast. The planet falls toward the black hole. The Ood close in on Rose and the crew, and the voice of the Beast declares its freedom. To be continued.

The story was well-received and compared to an entertaining science-fiction B-Movie like Stargate or Event Horizon, though some reviewers said they were kind of tired of losing the TARDIS. Still, you can’t very well have an instant escape vehicle sitting there. The story was tense and intriguing, the characters well-drawn, and the idea of an evil force taking control of a telepathic race a true science-fiction plot. It was a Base Under Siege story, Doctor Who’s version of an Old Dark House story. Some sound effects came from the 1993 movie Doom. The ship was based on the Nostromo from Alien. The voice of the Beast was provided by Gabriel Woolf, who played the evil Sutekh in Tom Baker’s Pyramids of Mars in 1975.

The planet was originally named Hell. Too obvious? The power source below, the Doctor muses, would have to be six to the power of six every six seconds. The Ood were marvellous. They were inspired by the Sensorites of the First Doctor, to whom they are related. Originally, it was supposed to be the Slithereen, but they might have distracted attention from the pioneering humans. The Ood were especially creepy speaking in unison. More than once in the course of events they said something that sounded like a threat, but it was only their translation orbs malfunctioning and what they meant to say was benign, so when they actually began intoning the words of doom, it was twice as frightening.