Helen Towers

 was the niece of Sandra Jane Rimdelle. Nyssa and Hannah Bartholemew met her in the orangery. She knew that Nyssa was one of the others, and wanted to know what she was. She was interested in cultivating plants. She felt that something was wrong. She could sense the Streamroller Man. She talked about Shadowspace. When she was unconscious she started speaking of an experiment. She was an intra-dimensional physicist. (AUDIO: Masquerade)