Past Reckoning (short story)

Summary
The Fifth Doctor visits his old friend David Gosthorpe, a scientist who made some of the greatest inventions in the universe. David's inventions are threatened when his evil sister starts to use them for her own pleasure. With Nyssa trapped inside her evil games, the Doctor must find a way to stop Ellen Carter's new power from spiraling out of control.

Characters

 * Fifth Doctor
 * Nyssa
 * David Ghosthorpe
 * Ellen Carter

Continuity

 * The Doctor says to Nyssa, "I'm a Time Lord. I walk in eternity." The Fourth Doctor previously told Sarah Jane Smith. (TV: Pyramids of Mars)
 * Nyssa suggests that she and the Doctor go and see Tegan now that they are on Earth. (TV: Time-Flight)