When Jake Green returns to his Kansas small-town home Jericho, where his dad Johnston is mayor, everyone is preoccupied with petty private business and family matters, but that changes drastically after a completely unexpected explosion. It soon becomes clear there has been a nuclear attack, but neither by whom nor on which scale. Suddenly life in Jericho, and as the inhabitants gradually discover all over the disintegrating USA, becomes a more primordial struggle for survival, where unexperienced dangers, primitive as well as technological, have to be weighed against pressing primal needs, such as food, fuel and self-defense against plunderers, invaders and even each-other. Jake, whose private story like that of other main characters slowly becomes disclosed to us, proves extremely resourceful and a smart hero, while his father's mayoral authority and even that of the only available medical professionals is soon challenged and undermined, criminal potentials are tapped into by circumstances and good people must rise to the daunting occasion assertively or perish. Even when contact is made with neighboring surviving towns, desperate rivalry soon cancels out solidarity.
The fallout from the nuclear blast in Denver will hit Jericho in an hour and Jake has to get the residents inside. The official shelter is not adequate and Jake must find another shelter to protect them. Emily faces troubles of her own while being picked up by who she thinks are two officers.
After seeing a broadcast via satellite from Asia, Jake gathers a group of people together for information gathering. After finding out that there is information out there, Jake suggests having four search parties to go out to get a better understanding what is going on outside of Jericho. The search parties set off in four different directions.
Jake finds a stranger who is sick with radiation poisoning and he must make a decision whether or not to help him. The hospital’s generator is running out of gas and the residents find that their supplies are also running low.
The children of Jericho start to return back to school. A power line that has fallen causes an accident on the playground when the power returns. Jake has an argument with his mother regarding a secret that Jake hasn't disclosed to his dad.
Hawkins must step in when an argument between Jake and an adversary becomes heated. After an electromagnetic pulse leaves Jericho in the dark crime runs rampant. Later, Jake is held at gunpoint and is rescued.
The slick gang leader Jonah bails Mitchell out of jail and agrees to give back the food that his bandits stole and agrees to keep out of Jericho. This plan strays off-course as Jonah negotiates new terms involving Jake and Emily.
Jake and Eric head out of Jericho to the nearby town of Rogue River to try and acquire some medicine for their father. While the brothers are at the hospital they encounter a combative group of individuals who call themselves Ravenwood. The brothers find that they’re trapped and must find a way back to Jericho.