Dopo che un disastro nucleare causato da diversi attacchi terroristici ha spazzato via gran parte del Nord America, gli abitanti di una piccola città del Kansas devono fare i conti con una realtà molto diversa.

Le ricadute dell'esplosione nucleare a Denver raggiungeranno Jericho entro un'ora e Jake deve portare gli abitanti al riparo. Il rifugio ufficiale non è adeguato e Jake deve trovare un altro riparo per proteggerli. Emily deve affrontare i propri problemi mentre viene prelevata da quelli che crede essere due agenti.

Dopo aver visto una trasmissione via satellite dall'Asia, Jake riunisce un gruppo di persone per raccogliere informazioni. Dopo aver scoperto che ci sono informazioni disponibili, Jake suggerisce di formare quattro squadre di ricerca per capire meglio cosa sta succedendo fuori da Jericho. Le squadre di ricerca partono in quattro direzioni diverse.

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.

I bambini di Jericho ricominciano ad andare a scuola. Una linea elettrica caduta provoca un incidente nel cortile della scuola quando torna la corrente. Jake litiga con sua madre riguardo a un segreto che non ha rivelato a suo padre.

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.

Some of the residents of Jericho are concerned that Gray's actions may actually make Gray the new mayor. In other news, Mitchell claims that Jonah is the killer under much speculation.

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.

Jake, his dad, Heather and Dale visit Black Jack to try and find the parts needed to fix the windmill. Sarah goes home with Hawkins against the rest of his family's wishes.

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.

Roger gets desperate after Gray kicks the refugees out of Jericho. Dale and Skylar collect on some debts. Hawkins continues his quest to find Sarah's contacts. Meanwhile, Hawkins begins the process of finding who's coming after him.

Jake finds that Hawkins has not been honest with the residents of Jericho about his past and holds him at gunpoint for answers.

Jake believes something more is wrong after Eric doesn’t return from New Bern. Jake and Hawkins go to New Bern and discover that Jericho is in danger.

The hostility mounts between the citizens of Jericho and New Bern. A handful of residents of New Bern are shot and injured after getting caught trying to steal from the Jericho salt mine.

The residents of Jericho and New Bern fight over precious resources and Gray must make a tough decision after the streets of Jericho are bombed.

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.