Peter Omir and Paul Ward conduct the internationally sponsored Mohole drilling operation to the Earth's core from the ocean floor, as the Seaview supplies the nuclear power for the highly developec drill heads. When Ralph Vendon, International Scientific Congress representative, visits the rig and discovers that Omir is concealing his discovery of an unknown element, Subterranium 116, that can produce boundless pure energy.

Omir locks him into a chamber and charges two S-116 cubes, causing him to disappear in a brilliant explosion of pure energy. Omir then enters the chamber to feed on the unholy glow; he is in reality an electrical Android, his back a circuitry bank, created by the now-subservient Paul Ward. Omir tells a horiified Paul that soon they will have enough energy to control the Universe. But aboard the Seaview, Captain Crane and Morton notice the shaft pressure is building to the red danger zone.

Soon it will blow, unleashing world-annihilating earthquakes, tidal waves, and volcanic eruptions. When Crane checks this with Omir, he rigs the dials to register false readings in order to continue collecting his S-116 from the drill cores.

Several hours later, when the Earth's core begins to erupt, Omir tries to calm Crane by telling him that it is only a pressure dome that will quell presently. But Crane has had enough and wants to plug the shaft.When he radios Van Druten at Geo physical Headquarters in New York, Omir tunes into the wave length and by exerting his electronic will forces Van Druten to order the drilling continued.

Crane is stunned. In the drilling control room, Paul tries to radio Crane for help against his electronic demon, but Omir shoots him unconscious with a charge from his forefinger. Learning of world-wide vollcanic activity, Crane finally decides to plug the shaft, no matter what Van Druten has ordered . Omir shows up aboard the Seaview, having walked across the ocean floor without getting wet, and knocks Kowalski out with a small charge.

As Crane prepores to blast the shaft with three MZ bombs Q_r!lir stops him by threatening~ his destruction. After Omir returns to his drilling, Crane orders the diving bell lowered as a decoy to cover Kowalski. Now recovered, Morton, and Jensen as they carry the three MZ bombs to Omiris instrumentation cave. Omir spots the bell and blasts it, but the three Seaview frogmen get inside the cave.

A rock falls onto the bomb packet, detonating the timer set to blow in an hour. By now Omir has discovered the scheme, and he puts out a force field that traps the three frogmen in the cave, isolating them from the shaft. Morton radios Crane, who offers Omir 50 men to aid his drilling if he'll release his men. Summoned by him, Crane goes aboard Omir's control room and finds Omir intends to plant circuitry in him to make him an Adroid. Mortor and Kowalski, meanwhile, manage to short out one side of the force field with laser pistols and plant the MZ bombs in the shaft.

Recovered now, Paul turns on Omir, and Crane looses a small hand bolt knocking both to the floor. Cued by Paul, Crane then crushes Omir's dark glasses as they protect his vulnerable photo sensory cell eyes. Ordering Crane from the room, Paul sets off two S-116 cubes, disintegrating himself and Omir. The explosion knocks out the cave force field's controls as well,
and Morton and Kowalski escape back to the Seaview. Crane flies in just as the shaft is closed in.

With many thanks once again to Linda Delaney for these super shots.