A huge burrowing machine tunnels out of control at ferocious speed, cutting clean through to the center of the earth, to the twilight world of pellucidar. Once there, Dr. Perry and David Innes are threatened by half human creatures, lizard-like birds, and man-eating plants.

A burglar falls for an heiress as she dies in his arms. When he learns that he has the gift of reincarnation, he sets out to save her.