In a sparsely populated town in 1974, ten years after a nuclear war has devastated the US, the townspeople have discovered a supply of canned food. However, they are waiting for Mr. Goldsmith, the town's leader, to return with a message from the mysterious and unseen "old man in the cave" who will tell them whether the food is contaminated with radiation. Some of the townsfolk want to take their chances and eat the food, but they refrain from doing so after seeing the disastrous harvest yielded when they failed to take the old man's advice about which farming areas were contaminated. When Mr. Goldsmith returns, he informs them that the old man has declared the food is contaminated and that it should be destroyed.
Shortly thereafter, a group of soldiers led by Major French enter the town and clash with Goldsmith as they try to establish their authority. The soldiers may or may not be representatives of the US government; Goldsmith claims that wandering packs of self-styled military men have previously intruded on the town and tried to establish authority—all unsuccessfully. French, meanwhile, reveals that there are maybe 500 people left alive between Buffalo, New York and Atlanta, Georgia, and also talks of small, isolated primitive societies on the shores of Lake Erie and in "what used to be" Chicago. He claims his job is to organize the region so that society can be re-built. However, Goldsmith believes that French and his men simply want to strip the town of its food.
A clash of wills ensues and, frustrated by Goldsmith's quiet and steadfast refusal to bend, French tries to dispel the townspeople's strange beliefs about the seemingly infallible old man in the cave and take control of the area. French tempts the townspeople with some of the food Goldsmith claimed was contaminated and many throw caution to the wind and partake. Everyone except Goldsmith eventually consumes the food and drink and Goldsmith falls into disfavor among the townspeople. After being bullied and threatened with his life, Goldsmith finally opens the cave door and it is ultimately revealed that in reality, the townsfolk have been using information from a computer the whole time. French rallies the townspeople into a frothing frenzy into destroying the machine, after which French leads the people into celebrating their new found freedom from this "tyranny". However, as Mr. Goldsmith had insisted, the "old man" was correct; without an authority figure to tell them which foods are safe, the entire human population of the town (including French and the soldiers) die—except for the lone survivor, Mr. Goldsmith, who somberly walks out of the now dead town