Ruth Horwitz

 was very work concious. She was jewish. She got anti-Semitic pen letters for three months. She was a physicist. She showed the letters to Peri Brown. Someone tried to kill her. Her room was ransacked. The Sixth Doctor asked her to tell the truth. She owned an alien eye that turned things invisible, but it was unstable so she couldn't use it for her desired result, to conceal whole armies to help invasions. (AUDIO: An Eye For Murder)