The Doctor transmits Sarah Jane and Harry down to Voga to cure Sarah Jane of the Cybermat's poison but Kellman's sabotage means he is unable to bring them back.
Quest roles:
Kevin Stoney(Tobias Vaughn), Christopher Robbie(Cyberleader), Ronald Leigh-Hunt(Commander Stevenson), Michael Wisher(Magrik), William Marlowe(Lester), Jeremy Wilkin(Kellman), David Collings(Vorus), Brian Grellis(Sheprah), Melville Jones(First Cyberman)