Past Reckoning (short story)

Summary
The Fifth Doctor visits his old friend David Ghosthorpe, 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 line "I'm a Time Lord. I walk in eternity" was first used in DW: Pyramids of Mars.