A pair of agents from the Office of Scientific Investigation (OSI), Dr. Jeffrey Stewart (Richard Carlson) and Dr. Dan Forbes (King Donovan), are sent to investigate a local appliance store. All of the store's clocks have stopped at the same time, while metal items in the store have become magnetized. A source for this is traced to an office located directly above the store, where various scientific equipment is found, along with a dead body. There are also signs of radioactivity, but the exact cause of the store's anomalies is clearly no longer in the room or even in the immediate area.
Investigation and a request for citizen input eventually leads to an airline flight carrying a scientist, Dr. Howard Denker (Leonard Mudie), who has developed signs of radiation sickness related to something he is carrying in a heavy briefcase and which he clutches irrationally. Before dying, he confesses to experimenting with an artificial radioactive isotope, serranium, which he had bombarded with alpha particles for 200 hours (8 days and 8 hours). Unfortunately, his so-far microscopic creation has taken on a life of its own: the new isotope must absorb energy from its surroundings every 11 hours; in the process it doubles its size and mass each time, releasing deadly radiation and incredibly intense magnetic energy.
The OSI officials realize that, with its rate of growth, it will only be a matter of weeks before the isotope becomes heavy enough to affect the Earth's rotation on its axis, eventually causing it to break out of orbit. They also discover that the isotope is impervious to any known means of destruction or to rendering it inert. The only answer appears to be using a Canadian experimental power generator, dubbed the Deltatron, being constructed in a cavern under the ocean. The hope is that bombarding the isotope with so much energy in one surge that it will neutralize itself with its own "gluttony".
The two governments agree on this proposal, and the isotope is transferred to the Deltatron project, but there is a last minute objection from the engineer in charge. With no time left, the lead OSI agent, Dr. Jeffrey Stewart, commandeers the huge device, a cavern-filling, multi-story machine. He risks his life by activating it, barely escaping just before sealing off the cavern. The machine powers up and the isotope is successfully pushed beyond its limits, completely destroying it, but the Deltatron has been destroyed in the process. All trace magnetism which it had been produced after every energy absorption has now disappeared.
The Earth has been saved from destruction by the efforts of the Office of Scientific Investigation (OSI). Life returns to normal, as shown by lead OSI agent, Dr. Jeffrey Stewart and his pregnant wife Connie (Jean Byron) completing the purchase of their first house and moving in shortly thereafter.
What are they investigating?
Appliance store