When the expedition broke into groups to explore the tombs, he and Jamie McCrimmon explored the weapons testing room, where they found a Cybermat. They manipulated some buttons that showed some hypnotic pictures on a screen. Haydon wanted to try an experiment and had Jamie push some controls. Just as the Second Doctor, Victoria Waterfield and John Viner entered, a Cyberman dummy came into the room and a weapon came out of the back wall. Haydon was in the path of the dummy and was shot and killed by the weapon. (TV: The Tomb of the Cybermen)