The Seventh Doctor meets Light, a traveler who journeyed through the universe making a catalogue of life. After Lights awakes from a millennia long sleep he notice the life on Earth has envolve. With everything life on Earth had changed, his catalogue was ruined and Light decide to prevent all life to change again. During these process he turns Lady Gwendoline and her mother Mrs Pritchard to stone.
This was the final shot filmed for the classic series of Doctor Who before it was cancelled