The Doctor, Harry and Lester try to destroy the Cybermen's relay device, while the Vogans prepare to destroy Nerva even though Sarah Jane is still on board.
Quest roles:
Kevin Stoney(Tobias Vaughn), Christopher Robbie(Cyberleader), Ronald Leigh-Hunt(Commander Stevenson), Michael Wisher(Magrik), William Marlowe(Lester), David Collings(Vorus), Brian Grellis(Sheprah), Melville Jones(First Cyberman)