"The Doctor indicated it was more complicated then just a trigger," Romana commented.
"Secondary switch, tied to removing the first one," the Master explained. "Designed to fool the mind into making a memory or fear actuality. Convince the body it's real and and it is, to the point of death. Same basic principle as the Keller Machine, remember that, Doctor?"
"And you went ahead an pulled it anyway," Romana said, tightly.