The young people press themselves against the wall and let the deranged Cyberman stagger past. Captain Turner leads the UNIT soldiers into the sewer. They encounter the Cybermen and attack with grenades. Private Perkins is killed in the fighting but two of the Cybermen are destroyed. The other attacks Jamie as he escapes and is destroyed by the UNIT soldiers.
The Doctor continues to inspect the IE circuits. The Brigadier is ready to go to Geneva but it will take days for them to act.
Packer reports the UNIT attack to Vaughn, but the Director is not concerned. They will soon control the entire world. Watkins is brought to him with the improved Cerebrator. Vaughn turns the machine on Watkins, who crumples in terror. Watkins calls Vaughn a sadistic megalomaniac and threatens to kill him. Vaughn hands Watkins a gun and eggs him on to shoot. But the bullets simply bounce off the Director.
Benton reports to UNIT that he has spotted Professor Watkins. The Brigadier orders him rescued. The rescue destroys Vaughn's plans to mass-produce the Cerebrator and he kills Gregory.
The Doctor, spurred by Watkins, figures out that the extra circuits are emotional circuits. As the Cybermen disperse through the sewers, The Doctor figures out that the invasion spaceship behind the moon will broadcast a signal to other ship around the Earth, which will activate the extra circuits in the IE hardware. They will create a cyberhypnotic force that will put all of humanity under their control. He and Zoe figure out a depolarizer to block the cyber signal but are unsure if they will have time to make them.
They cyberships move into position for the invasion, now minutes away from activating the signal.
As dawn breaks, the Doctor and his friends await the attack. Suddenly, a strange pulsing noise is heard. All around London, people collapse under its influence, including the Doctor.
Covers fly off of sewers. Hundreds of Cybermen emerge. As the hypnotic signal continues to sound, they march in formation down the very streets of London.