Vanguard (The Spirit Trap)

Mrs Vanguard was a medium who held seances for the people of London. Her ceremonies were apparently so compelling that they attracted the watchful eyes of Henry Gordon Jago and Professor Litefoot. Jago believed that the seances were a theatrical trick, but after thorough investigation, people who had met Vanguard during one of her ceremonies had become "possessed".

She was actually communicating with spirits from the 49th century. They had requested her help in bringing them bodies so they could reach their final goal: to possess her majesty, the Queen herself. It turned out that Mrs. Vanguard was under the control of the spirits and was actually an innocent civilian, pretending that she had the powers to speak to those dear to the people who visited her. (JAL:  The Spirit Trap)