Dr. Steven Sorenson (Dana Andrews) and his wife and fellow scientist Dr. Maggie Sorenson (Janette Scott) plan to utilize the geothermal energy of the Earth's interior by detonating a powerful thermonuclear device deep within the Earth's core. Despite warnings by Maggie's ex-flame and fellow scientist Dr. Ted Rampian (Kieron Moore), Dr. Sorenson proceeds with the experiment after he secretly learns that he is terminally ill. This experiment causes a crack within the earth's crust and threatens to split the earth in two if it is not stopped in time.