Helen Fitzmaurice
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Helen Fitzmaurice was Lawrence Grainger's niece and Edward Grainger's cousin. According to Edward, his father considered her "unbalanced". Margaret Pollard's mother called her a "liability". She often had moments where she was unaware of her surroundings.
Helen had an imaginary friend, Ahnji, who was in reality an alien that had been trapped in a graphaphone. When he was freed by the Third Doctor, Helen was cured of her strange behaviour. (PROSE: Echoes)