During an atomic war, pockets of liquid uranium 235 stored beneath an atomic powerhouse are brought nearer to the surface when an enormous bomb destroys the city above it. Hundreds of years later, the war is forgotten and civilization has been rebuilt.
A man digging a tunnel near this powerhouse uncovers one of these pockets and quickly dies from radiation burns. The doctors are mystified by his injuries, since atomic energy (and its effects) has become a myth, and attributes the death to a heart attack. The man's nearby house and the property around it are inherited by his niece, Janie Nichols, who chooses to rent it out. The man handling the estate spends a night there and is terrified by the strange light phenomenon caused by the radiation's spectacular interaction with various substances in the house, and flees in panic before the night is through. Over the next few years the house is let to two groups of tenants, each of which is frightened by the lights and obtain strange burns, and leave the house hurriedly. The house soon gains a reputation for being haunted, and while it sits empty the vibrations created by these radioactive interactions seal up the ways to the surface.
Janie and her husband Peter decide to live in the house for a while in an attempt to show to the locals that the house's reputation is undeserved. They desperately need tenants and the added income that would generate, and are renting out their home in the city until they've put an end to the rumors surrounding the country house.
While getting ready for bed their first night there, they argue about the existence of the legendary "atomic age" that supposedly existed before the harnessing of nuclearicity. Janie tells her husband that an "atomic powerhouse" — of which only mounds remain — once existed over the site where her uncle tried to dig a tunnel, and that may be the cause of the strange occurrences in the house. He points out to her how ridiculous the atomic myth is, that it is unbelievable that any power source could last for hundreds of years, and that if such a great civilization existed it would not have disappeared virtually overnight. He finishes by extolling the virtues of the current method of generating power, nuclearicity, which is clean, safe, and makes sense. His wife, however, remains nervous, and allows him to share the bed despite her difficulty in sleeping if there is anyone else in the room.
Peter discusses with his wife the possibility of clearing away the mounds where the supposed atomic powerhouse once stood, and she asks where he thinks he's going to get the money and the labor force — they're hard up as it is, and the locals are the least likely to come anywhere near the house. He admits the impracticality of this, and suggests that he could hire someone from a university to give their opinion of the mounds.
That afternoon they fly in their fast, nuclearicity-powered car into the city to do a few errands before letting the tenants have their house there. Janie bumps into the wife of a well-known physicist, Professor Leard, and invites them over for the weekend to look over their country house that is "haunted by atomic energy." She later reports this to Peter and explains how the academic community has recently been reevaluating the atomic myths, and come to the conclusion that such a method of generating power is theoretically possible. The current method, nuclearicity, is dependent on activating one block of material by putting it next to an already activated block — where the first activated block came from, as well as how nuclearicity was invented in the first place, remains a mystery and they believe perhaps its origin is connected to atomic energy. She also reports that Leard has offered to have the mounds excavated at the university's expense.
Days later, while Leard and his team are working, Janie insists that her husband take her into town to go shopping. On the way, she confesses that she expects them all to die as her uncle did, but hopes that before they do that they've cleared enough of the mounds away to make the house livable again — she insisted on the shopping trip to get them out of danger, as well as far away from the upcoming tragedy. He is horrified by her selfish and murderous attitude, but she calms him down by explaining that they're aware of the danger, have taken all possible precautions, and that they're the only ones qualified enough to handle the situation.
That afternoon on their return trip, they phone the country house expecting no answer. When Leard indeed fails to do so, Janie is suddenly struck by what she has done. They arrive at the house, and circle the area in their aircar, noticing that the mounds are gone and no one is around. Her husband tries to calm her and phones the university. They are both relieved when Leard answers. He explains to them that they cleared up all the radioactive substances and hurriedly packed it away into safe containers and returned to the university with it. He briefly mentions what a powerful and potentially dangerous material it is, and says they could even create devastating bombs with it. He offers to pay the Nichols $5,000 to show the university's gratitude, and to make plain they purchased the substance from them. He also says that there will be no further strange phenomenon at the house.
In her excitement Janie hangs up on him and insists that Peter land the car. She goes into the house and puts the "For Rent"sign up again, explaining that she finds life in the country too dull. They immediately begin the trip back to town. Their house there is already up for rent, but they intend to get there before their tenants do, and offer them their country house instead.