Dr. Stephen Sorensen (Dana Andrews, The Satan Bug) and his wife and fellow scientist Dr. Maggie Sorensen (Janette Scott, The Day of the Triffids) 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 from Maggie's ex-flame Dr. Ted Rampion (Kieron Moore, Arabesque), Dr. Sorensen proceeds with the experiment after he secretly learns that he is terminally ill. This experiment uses a crack within the Earth's crust and threatens to split the Earth in two if it is not stopped in time! Heralding the boom of disaster movies in the 1970s like Airport and Earthquake, this rippingly entertaining '60s sci-fi adventure will shake you to the very core!