When John Farrel began interfering with his plans, the Master turned the heat (which would cause the doll to activate) in Farrel's car to maximum, and gave him the troll doll, planning for it to kill him. However, just as the doll began to activate, Farrel switched off the heat and opened the windows, causing the doll to deactivate. He later showed it to his wife Mary, and when she left to make coffee, he set it on the heater. It activated and killed Farrel, but when it tried to escape, it deactivated.
When the Third Doctor and Jo Grant visited Mary after the murder, she gave them the doll. The Doctor's tests on the doll proved inconclusive, and he later left for Farrel Plastics with Brigadier Lethbridge-Stewart, leaving it next to his Bunsen burner.