Simon Valdac

 was the guest of Sandra Jane Rimdelle. He wondered if Voltaire had really recommended meeting with the Fifth Doctor. He later went for a walk with Hannah Bartholemew. He realised that they obeyed Helen Towers when she told them to get back to the house. He told the Doctor about Shadow Space. He was a neuroscientist. When he went back to home-dimension, he helped Nyssa to get everyone out of Shadow Space, and recognised the Tendragon. (AUDIO: Masquerade)