Written by Robert Holmes
Directed by Michael Hart
The TARDIS materializes on a space beacon just before it is attacked by pirates, who use explosive charges to break the station into separate pieces for easier transport. Trapped in a different section than the TARDIS, the travellers can only watch as it is flown to where the pirates will plunder it of the precious mineral argonite. They then witness a conflict between the pirates and the Interstellar Space Corps.
Meanwhile, the Interstellar Space Corps are relentlessly tracking the pirates, but making little headway. General Hermack of the ISC is convinced that the leader of the pirates is a crusty and eccentric prospector named Milo Clancey, but in reality the pirates leader is a man named Caven. Caven has a secret base on the planet Ta. The planet is under the dominion of the Issigri Mining Corporation, a company created by Clancey and his ex-partner, Dom Issigri. The Corporation is now run by Dom's daughter Madeleine, following the murder of her father, with Clancey being the obvious suspect.
Madeleine is reluctantly in league with Caven, though unbeknownst to her, her father is not dead, but the captive of the pirate leader. The Doctor and his friends, along with Milo, manage to free Dom Issigri, and when Madeleine discovers Caven's plan to kill both her father and Milo, she finally helps to bring him to justice. The time travelers are given a lift back to the TARDIS by Clancey and head on their way.