is destroyed by the gravitational pull of Mondas. The emotionless Cybermen state that the lives of the crew are irrelevant to them. The Cybermen explain that Mondas is absorbing energy from Earth and will soon destroy it. They propose to take humans back to Mondas and turn them into Cybermen. General Cutler, the Snowcap base personnel and the Doctor's companions mount a resistance to the Cybermen, overpowering them and killing them with their own cyberweapons. Cutler plans to destroy Mondas using a Z-bomb, one of a series of powerful nuclear bombs that are placed at strategic points around the world, and contacts Space Command HQ in Geneva. The chief scientist Dr. Barclay expresses concerns that the radiation caused by the exploding planet would cause immense loss of life on Earth, and Ben argues that Mondas might destroy itself anyway when it absorbs too much energy. Suddenly, the Doctor passes out, ill. Faced with dissent, Cutler orders Ben to be imprisoned in a cabin with the Doctor. Ben escapes and, with the help of Polly and Barclay, sabotages the Z-bomb rocket. Cutler attempts to fire the Z-bomb, but the engines fail on the launchpad. As Cutler threatens to kill Ben, Barclay, and the Doctor, who has now regained consciousness, he is killed by a new squadron of Cybermen. The Doctor, who explains to Polly his body is “wearing a bit thin”, and realising that Mondas is approaching destruction, attempts to mediate with the Cybermen, offering them a home on Earth. The Cybermen take Polly and the Doctor back to their spaceship as hostages. As the Cybermen take over Space Command in Geneva, the Doctor realises that their plan is to destroy the Earth with the remaining Z-bombs, thus saving Mondas. The Cybermen order the humans to disarm the Z-bomb and send Ben, Barclay, Haines and Dyson into the bomb chamber. Ben surmises that the reason the Cybermen send humans to do this work is that the Cybermen are highly susceptible to radiation. Using radioactive rods from the reactor chamber as a weapon against the Cybermen, Ben and the crew regain control of the base. Just as more Cybermen enter the Tracking Room, Mondas explodes. Disconnected from their power source on Mondas, all the remaining Cybermen die. Geneva Space Command contacts the base to announce that the Cyberman threat has ended. Ben frees the Doctor and Polly from the Cybermen's spaceship. The