Troll doll

When Colonel Master, a.k.a., took charge of Farrel Plastics, he produced a troll doll out of plastic, which was animated by the Nestene Consciousness.

The doll was activated by a pre-set temperature.

History
When John Farrel began interfering with his plans, the Master turned the heater controls in Farrel's car to maximum (which would cause the doll to activate), and gave him the troll doll, planning for it to kill him. However, just as the doll began to activate, Farrel switched off the heater and opened the driver's window, causing the doll on the back seat to become dormant.

Farrel later showed the doll to his wife Mary, and when she left to make coffee, she left it on top of a radiator. It activated and killed Farrel, but when it tried to escape via the window, where it would later be found by Mary, it deactivated.

When the Third Doctor and Jo Grant visited Mary after the murder, she told them how she had later found the doll under the window curtain — saying it was almost as if the doll was seeking a way out. The Doctor brought the doll back to his laboratory at UNIT H.Q., where his tests on the doll proved inconclusive, and he later left for Farrel Plastics with Brigadier Lethbridge-Stewart, leaving it next to his Bunsen burner.

When Captain Mike Yates used the burner to make cocoa, the doll activated and attacked Jo. However, Yates shot the doll several times with his pistol, destroying it. (TV: Terror of the Autons)

Behind the scenes

 * The troll doll was played by Tommy Reynolds during scenes in the story involving CSO, who remained uncredited both on-screen and in Radio Times.