Terror of the Vervoids

From: http://www.bbc.co.uk/doctorwho/classic/episodeguide

The distraught Doctor gives the court his evidence for the defence. He chooses an incident from his own future, in which he and his companion Mel arrive on the space liner Hyperion III in response to a distress call. There they battle against and ultimately destroy a hostile race of alien plants, the Vervoids, while also helping to thwart a mutiny by the ship's security officer, Rudge.

83 out of 97 (85.6%) raters say this story requires a previous story.