At the Earth's Core

Peter Cushing stars as Dr. Abner Perry, a Victorian scientist who has invented an enormous boring machine. Accompanied by his financial backer David Innes (Doug McClure), he undertakes an experiment that will take him deep into the Earth's crust. Unfortunately he doesn't know the strength of his own creation, and the machine carries them all the way to the enormous cavern at the center of the Earth. There, the scientists discover an incredible world populated by a prehistoric human race. The humans are ruled over by despotic, telepathic bird-monsters who use them for food and labor. The visitors decide to attempt to free the humans, while the charms of one slave in particular (Caroline Munro) do not go unremarked. (official distributor synopsis)