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In the fourth episode of the seven-part story "Inferno," the Doctor (Jon Pertwee) is still trapped in an alternate universe, where the fascist government of England insists upon pursuing Project Inferno, intended to find new energy sources at the center of the earth. Alas, the Doctor is armed with the foreknowledge that this supposedly beneficial project will result in the destruction of the world. But inasmuch as the government is now a dictatorship, no one will listen to the Doctor's grim prognostications. Written by Don Houghton, "Inferno, Episode 4" first aired on May 30, 1970.