After a nuclear disaster caused by several terrorist attacks wipes out most of North America, residents of a small Kansas town have to come to terms with a very different reality.

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.

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.

The residents of Jericho receive a visit from a group of questionable outsiders and they realize that they need to form a plan to keep the outsiders out. Emily has a dream about her wedding morning to Roger. She wakes up and realizes that he is probably dead.

Supplies are dropped by air into Jericho and the Green's and Hawkins think that they know where they came from. Jonah Prowse returns to Jericho causing even more trouble.

The lives of Jake and Hawkins are explored during this flashback episode. This episode begins 36 hours before the bombs went off. Sarah is introduced and is associated to Hawkins. Jake had been living in San Diego.

While on a hunting trip outside of Jericho, Jake, Stanley and Mimi find themselves in a dangerous situation when they run into some strangers. Meanwhile, Hawkins realizes that his family is in danger because of him. Emily and Roger work on their relationship.

After a company of Marines show up, the town of Jericho has hopes that life will finally start to return to normal. However, their behavior raises Jake's and Johnston's suspicions.

After April collapses and goes into early labor, Jake makes Kenchy face his problems so that they can save April. The wind turbine arrives from New Bern but Heather does not return. Jericho makes a deal with New Bern to send ten of their people to New Bern to make more wind turbines as long as New Bern receives a percentage of their spring crop.

The battle with New Bern ensues, with Jericho residents out-manned and out-gunned, but not outsmarted. Jericho gains the upper hand but suffers a significant casualty. A friend of Jake's sends help from an unexpected source.