Doctor Who The Pirate Planet Part 1

The Key to Time tracer points the Fourth Doctor and Romana to the cold and boring planet of Calufrax, but when they arrive they find an unusual civilisation living in perpetual prosperity. A strange band of people with mysterious powers known as the Mentiads are feared by the society, the Doctor discovers that they are good people but with an unknown purpose. He instead fears the Captain, the planet's leader and benefactor. After meeting the Captain on the bridge he learns that they are actually on a hollowed-out planet named Zanak, which has been materialising around other planets to plunder their resources.

After repairing Zanak's engines, which were damaged when the planet materialised in the same place as the TARDIS, the Captain plans to take Zanak to Earth. The Doctor finds the true menace controlling the Captain is the ancient tyrant Queen Xanxia, disguised as the Captain's nurse, who uses the resources mined from planets in an attempt to gain immortality. Her physical body sits between Time Dams, devices that hold back the ravages of time, as she is old and near death, and a younger version of her is projected via a solid 3D device. Despite the Captain's apparent insanity, he is a calculating person who plans to destroy Xanxia. The Mentiads learn that their psychic powers are strengthened by the destruction of entire worlds beneath their feet: As the people on the planets die, their combined psychic force boosts the Mentiad's power.

Throughout Zanak, the Key to Time locator has been giving odd signals that seem to indicate that the segment is everywhere. Once the Doctor and Romana see the Captain's trophy room of planets, they conclude that Calufrax itself is the segment that they are looking for. The Captain's intends to use the gravitational power of all the crushed worlds to essentially drill a hole through the time dams, bypass its fail-safe mechanism, and let time move forward so the queen dies. They use the TARDIS to once again disrupt Zanak's materialisation around Earth while the Mentiads sabotage the engines. Xanxia kills the Captain when he finally turns against her and his plan fails. As Calufrax is not a real world, its mass is different and Zanak is unable to consume it. The Doctor, Romana, and the Mentiads destroy the bridge and Xanxia, ending the devastation caused by Zanak's travels. The Doctor rigs the system to drop the crushed worlds into the centre of Zanak where they'll expand and fill it, except for Calufrax which he sends it off into the time/space continuum where they pick it up later.