The three scientist Mr. Edward Malone, Mr. Peerless Jones and Professor Challenger come together to build a machine that can drill deep into the earth. When the machine's construction is finally completed the drilling starts, and it will not stop until the earth's mantle is reached. Everything goes well for the three men, until they reach something into the earth that threatens to destroy their excavation. What is the reason for the excavation? What is threatening to destroy their mission and why? How is everything going to end? Will the three scientists manage to complete their goals, or it will all be one great failure? This science fiction is the fourth Professor Challenger story and it was first published in 1928.