The Cybermen intend to crash the bomb-laden Nerva Beacon into Voga.
Fortunately, Harry is stopped by Lester. The Doctor awakens and conceives a plan. Stevenson will go on and create a radar trail, while the rest use the cross shaft to surprise and attack the Cybermen with gold. The Doctor and Harry jump the two Cybermen, trying to push gold dust into their chest plates, but the Cybermen are too strong, and Harry and the Doctor are forced to retreat. Lester leaps onto the Cybermen and undoes his harness, the explosion killing himself and the Cybermen.
With the loss of contact, the Cyber-Leader orders immediate detonation. Sarah tries to stop them but is thrown to the floor. However, when the button is pressed, no explosion follows. The Doctor has managed to disarm the countdown device, which allows him to release his harness safely. With Sarah tied up, the Cyber-Leader now plans to send Nerva, loaded with more Cyberbombs, into Voga’s centre to destroy it.
Magrik tells Vorus that the Sky Striker is ready, but before he can launch it, the Doctor asks them to give him fifteen minutes to transmat to Nerva and deal with the Cybermen himself, armed with a bag of gold dust. If he does not contact them in that time, they can launch the rocket.
The Doctor reaches Nerva and frees Sarah while the Cybermen are loading the bombs. He takes the Cybermat and its control box, filling the Cybermat with gold dust. He sends the Cybermat to attack a Cyberman, injecting him with the dust and killing him. As Nerva begins to move towards Voga, Vorus sees this and tries to fire the rocket. Tyrum shoots Vorus, but as the Guardian dies, he triggers the launch.
The Doctor and Sarah’s attack on the remaining Cybermen fails; the Doctor is forced by the Cyber-Leader to tie himself and Sarah up and they are left to perish in the crash. However, the Sky Striker is approaching just as fast. The Doctor manages to untie them both with a trick learned from Harry Houdini, and contacts Voga, instructing them to steer the rocket towards the Cybership that is just leaving. The Sky Striker veers away from Nerva and destroys the Cybership instead. However, the beacon is still on a collision course. The Doctor unlocks the gyro controls, skimming Nerva just above Voga’s surface until they reach the other side of the asteroid and open space.
The TARDIS materialises in the control room just as Harry arrives via transmat. The Doctor tells his companions to hurry up; he’s received a message from Brigadier Lethbridge-Stewart through the space-time telegraph the Doctor left him, which means it is a grave emergency. Although Harry asks if they should say good-bye to the Commander, Sarah tells him not to argue. The three rush into the TARDIS and it dematerialises.