The Doctor overloads the reactor and tells the younger Silurian that the area will be irradiated for at least 25 years. The Silurians re-enter the caves to hibernate until the danger has passed. Since the mechanism is faulty, the younger Silurian will stay awake to operate it and sacrifice his life. The Doctor and Liz repair the reactor. The younger Silurian realises he has been duped into sending his race back to sleep. He attacks the Doctor but is shot by the Brigadier.