During the expedition to the Sense Sphere, he found the planet was rich in molybdenum, forcing the Sensorites to attack his mind. Unlike Maitland and Carol, who were put in a deep sleep resembling death, John's mind was opened and he became insane. Along with the rest of the crew, he was held prisoner on their ship. He was eventually calmed by Susan Foreman and Barbara Wright and the Sensorite scientists agreed to restore his mind on the Sense Sphere. His open mind saw evil in the City Administrator. His mind was eventually restored, and with Susan's help, he identified the Sensorite plotting against the humans, the City Administrator. He was allowed to return to Earth. (TV: The Sensorites)