Arriving on Tara, Romana locates the fourth segment of the Key to Time with ease, but is captured by the scheming Count Grendel who wants the throne of Tara for himself.
The Doctor attempts to enter to the castle to prevent the marriage of Romana to Prince Reynart and thus thwart Grendel's dastardly plans to rule Tara.
Grendel kidnaps Prince Reynart and seems set to be chosen as Tara's monarch when Reynart fails to arrive at his coronation. But the Doctor has a plan to scupper the Count's scheme.
While Romana makes her escape from the castle, the Doctor is lured to a meeting with an android duplicate of her that is programmed to kill him.