The Second Doctor, Jamie and Zoe return to Earth and meet up with an old friend, former Colonel and now Brigadier, Lethbridge-Stewart – now in charge of the newly formed UNIT who are investigating electronics manufacturer International Electromatics. IE’s managing director, Tobias Vaughn, is working with the Cybermen. He is planning to transmit a hypnotic signal through IE’s products, leaving the Earth paralysed and allowing the Cybermen to emerge from the London sewers and take over…