The story begins on a regular December day of the year 1960 in a sleepy Florida town named Fort Repose. Florence Wechek, a local telegraph manager, watches the morning news while she makes breakfast. The newsreader talks about how the Russians are releasing more Sputnik satellites and that the Middle East is to be in some sort of a crisis. One of her neighbors, Randy, receives a telegraph from his brother Mark Braggs about the impending arrival of his wife and children with the ender being “Alas, Babylon”. The ender implies that a nuclear war will wage and that Fort Repose will be safer than other places when that moment arrives. It is a rather private family code. Soon, Randy plans to make a visit to Orlando while Florence, on the other hand, gossips about the ender with Alice Cooksley. She looks it up on the Bible and finds out about the ender’s indication of imminent destruction. At noon, Randy arrives and meets up with his friend, Paul Hart, who is an ace pilot. He learns that the Orlando Air Force base is empty since the planes have been made ready for war at a short notice. His brother Mark shows up and tells him about the situation, giving him five thousand dollars for purchasing necessary commodities for survival. Mark goes back to Omaha and before leaving, requests his brother to look after his family. They bid farewell to each other and Randy travels back to his home at Fort Repose in Florida.
After going back to Fort Repose, Randy checks out the five thousand dollars while being bugged by Edgar Quisenberry. After that, he rushes to the supermarket to buy some meat, canned food and other necessary liquid consumables like coffee and an ample amount of water. The crowd at the market stares at him with awe as he lugs the large amount of goods he has bought. However against his wish, Randy resists the urge of telling them the reason behind his actions and rushes out. On the way, he reveals news regarding the incoming war to only one of his neighbors, Malachai Henry. The Henrys are a family consisting of Malachai, his father, Preacher and his sister Missouri along with Missouri’s husband, “two-Tone”.
The story quickly shifts to Randy who reaches home and meets up with his girlfriend Lib. He also receives a sudden visit from Dan who is a doctor. He warns both of them and they also set out to prepare accordingly. While sightseeing, Randy comes across Florence who immediately accuses him of spying. As they converse, the scene shifts to a war zone in mid air of the Eastern Mediterranean where the US pilots battle the enemy fleet but somehow end up accidentally bombing a missile on Syria. Soon after, Randy visits Lib at her place where his news about an upcoming war is concluded as a fake report. Meanwhile, Helen reaches Florida and Randy picks her and the children up and following this incident, missiles are shot from the inside of Soviet Union, signaling the beginning of the nuclear war.
The next chapter begins with Randy, Helen, Ben Franklin and Peyton waking up from sleep to an earthquake. It was apparently the result of two nuclear bombings that had occurred far away from them, in the South. One was dropped in Miami while the other was dropped in SAC. When they leave the house to see the conditions outside, they watch fighter jets flying over and soon, another explosion occurs at Tampa-St. Petersburg. Peyton happens to look at the direction of the explosion and is blinded by the light. Next, Randy rushes to the city only to see that the city has resulted into absolute chaos. People are seen creating crowds inside general stores and gas stations. All the local guests at the hotels have faces with confused expressions. Randy finds Dan in one of the rooms tending to a patient. He informs Dan of Peyton’s condition to which the doctor prescribes eye drops and resting in a dark room. Meanwhile, people gather to send telegrams. Edgar Quisenberry fails to take orders from the Federal Reserve Bank at Jacksonville since it has been blown up by a nuclear explosion. When the people start trying to push inside to withdraw money, he shuts the bank and shoots himself out of craze. Afterwards, on the day of the explosion, the Acting President states on the radio how they will be trying to take care of the present situation. Peyton regains vision and the Orlando explosion causes Fort Repose to suffer from a permanent blackout.
The whole town turns into an isolated land as due to the blackout, Fort Repose loses all sorts of technological and mechanical support. Randy, along with Malachai and Two-Tone, sets up a pipe to carry water from an artesian pump that draws supply from underground water. Helen helps by salting the meats in order to increase its shelf life. Randy has additional duties: he goes out to buy a pair of ten-pound bags of salt for two hundred dollars. Next, he heads up to the clinic to find the whereabouts of Dan. There, he finds Dan in the middle of broken medicine bottles while the local sheriff has been shot in the hallway. This had happened when a bunch of addicts attacked the hospital in search of morphine. After hearing about this, Randy makes Dan move in with him. The next scene occurs during a dinner at the Henrys’ when suddenly the radio announces the contamination of different regions including Omaha and Florida. On the sixth day of the attack, Lib’s mother, Lavinia McGovern, dies of diabetes due to lack of insulin. The local hotel burns down to ashes. Randy helps Lib and Bill bury Lavinia’s body and afterwards, they also move in with Randy. Four more months go by and even daily consumables like coffee and tobacco start to use up. The Henrys appoint Ben to deal with the predators who are stealing the family animals. Dan and Randy drive up to the park to trade scotch for coffee. They treat the radiation-poisoned people there and try to find the cause of it. It is decided that Porky’s radioactive corpse is to be buried the next day.
Burying Porky Logan’s body becomes a big trouble when they come across the situation of putting the radioactive body along with the radioactive jewels in a coffin that is made out of lead. It weighs too much and none volunteers to become one among the six other men to carry the coffin to the grave. This causes Randy to take a desperate measure to convince them: gunpoint. Meanwhile, Bill and Two-Tone Henry manage to make a still to make corn whiskey from abandoned car parts. The radio announces that the reserve officers alive within the Contaminated Zones are to assume authority of the areas they are residing in. Since Randy is a Reserve officer, he has to take control of Fort Repose. Helen starts to have hallucinations about Randy being her husband Mark and tries to kiss him. On that same night, Alice Cooksey and Florence make a good dinner comprised of wild plants. Randy and Lib walk alongside the river but return home after hearing an alarm. They find Dan staggering inside the house, weakened with bleeding bruises. He is fed and let to rest. When he regains enough strength to talk, he informs them about the thugs who beat and looted him. Randy goes back to Pistolville and with the help of Rita, sets up a trap to catch these thugs. After they return home, Lib and Randy make plans to get married to each other on Easter.
On the Easter Sunday, Preacher conducts the marriage rituals of Randy and Lib. The best man, Dan, comes in with a bandaged arm. The marriage is conducted under the Order no.4 published by Randy for marriage and birth certification. Randy then focuses his attention to capturing the thugs that had beaten Dan. To catch these thugs, they set themselves up as baits inside Rita’s truck while Bill McGovern, Malachai and Hazzard stand with guns loaded in hand. Soon they come to a dead end and two hooligans from both side spring up and attack. Although three of the hooligans are gunned down, one tries to escape but gets caught. Unfortunately, Malachai is shot in the chest and dies out of bleeding. The next day, the captured criminal is hanged. Upon the arrival of summer, life comes to a standstill when Admiral Hazzard’s ham radio breaks down and the only way of communication is not available anymore. Meanwhile, just when they were about to run out of salt, Randy finds a book written by his predecessors, which cites a source for salt. Following the book’s instructions, they come back with sacks of salt. On the other hand, Peyton takes Florence’s goldfish and uses it as bait to catch a big-sized bass. In the end, a makeshift school is set up and Dan delivers the first baby in town. Mark is declared dead and Paul Hart informs that the war has been won to which Randy barely reacts.