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.

The Cybermen force the Doctor, Stevenson and Lester to carry bombs to the centre of Voga while Sarah Jane, Harry and Tyrum decide to contact Vorus.

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.