In the premiere episode, Jake returns to Jericho after a long absence to claim a sum of money his grandfather put aside for him. With the past five years of his life shrouded in secrecy, Jake evades questions about his whereabouts.
It's only an hour before the fallout from the nuclear blast in Denver hits Jericho. Jake rushes people to get to the official shelter so that they won't get radiation poisoning. Unfortunately, the shelter is in disrepair and unusable, so they must come up with other protection quickly. Emily and Bonnie are held hostage.
After seeing a broadcast from Asia on satellite televison discussing the extent of the nuclear attacks, Jake suggests sending out four search parties for information gathering. The search parties go out in four different direstions.
Jake finds a stranger who is sick from radiation poisoning and helps him. Meanwhile, the gas for the generator is low so people have to take gas from their cars.
The TV, radio and phone lines come back on, but all contain only a prerecorded message telling people to stay where they are. The internet is back, but the townspeople are blocked from surfing it; it just has the same emergency message. But the connection is only temporary--it's off again by the end.
Missiles fly through the sky as the power goes off from an electromagnetic pulse. Allison is suspicious of her father's return home. The townspeople receive calls alerting them the federal government is shut down.
One of the townspeople, Gray, returns with information about other cities. Hawkins finds out his wife was seeing someone else in Washington; she is upset when he reveals to her that DC was wiped out. Jake tries to make a deal with Jonah. Johnston's infection gets worse. Jake goes packs up to go to Rogue River to get the medicine his dad needs.
Jake and Eric narrowly escape a militia that is raiding the hospital for supplies while getting medicine for Johnston in Rogue River. They meet a doctor there who they bring back with them. Meanwhile back at the house, Heather makes ice to help cool Johnston down. And Gray interrogates Hawkins, finding an FBI badge in his house.
The town wants to burn the bridge to keep the militia from Rogue River out, but the Mayor is against the idea. Emily thinks about how she was supposed to get married that day. The Mayor takes charge again and makes plans for preparing the town to defend itself.
Bombers drop supplies for Jericho, but when they realize the supplies are from the Chinese, Johnston collects the supplies to make sure they are safe for the people. Jonah tries to take some of the supplies for himself. Johnston tells Eric that April is pregnant.
Gracie is murdered and the town assumes it's Jonah and captures him. Johnston tries to save him, but this just helps Gray win the election. Gray is sworn in as the new mayor. Hawkins lies to his contacts saying he's been compromised and they know he's lying. Some refugees show up in town.
A flashback to before the bombs went off reveals information about Jake and Hawkins' pasts. Jake is trying to turn his life around and make an honest living, but because of his past he is running into problems and his friend, Freddie gets him involved in a dangerous mission for Raven-wood. Hawkins takes his family to Jericho under duress. Emily's fiance, Roger leaves for a job interview in Chicago despite Emily's protests.
Jake and Johnston go with Heather and Dale to a trading post. They are looking for a part that Heather needs to fix the local windmills so the town will have enough power for the winter. Dale goes along to try to trade for some supplies he can actually sell in his store. Meanwhile, back in town Sarah shows up at Hawkins' house and he brings her to stay with his family.
Jake, Stanley and Mimi leave town to go hunting for food. They encounter a truck that pushes them off the road and steals their supplies. Jake is pinned under a truck and Stanley's ankle is injured, so Mimi has to go for help.
As the town worries about not having enough supplies, some of the newcomers think about leaving. The Marines arrive with the promise to restore law and order to Jericho, but Jake discovers that they aren't really Marines. Meanwhile, Hawkins has a showdown with Sarah when she takes his family hostage in order to get the package from him.
April has a complication with her pregnancy and she needs a doctor, so Jake must force Kenchy to come back to the medical profession. When April loses the baby Eric is upset and he realizes that he's also afraid of losing her.
Gray decides to kick the refugees out causing a showdown between the townspeople and the refugees. Gray is shot in a struggle with Roger and Roger is banished from the town.
Jimmy tells Jake of his suspicions of Hawkins and takes Jake to Hawkins' house to prove it to him. Jake stays and ambushes Hawkins to get the full story from him.
When Eric does not return from New Bern with the other men, Jake senses something is wrong so he enlists the help of Hawkins and they go together to the town of New Bern to find him. When they arrive, they learn that Heather is missing as well. While looking for Eric and Heather, they discover that New Bern officials are planning an attack on Jericho to gain control of their salt mines. Jake is captured, but Hawkins manages to escape.
A group of citizens from New Bern come to steal from the Jericho salt mines and gunfire breaks out. As Gail works to help the wounded at the hospital, Johnston leaves to go find his sons. Maggie and Hawkins help break Eric and Jake out of jail and Johnston helps them as they head back to Jericho.
New Bern begins bombing the streets of Jericho with mortars in order to get Jericho to give them part of the salt mines and several farms. Mayor Gray Anderson wants to give them what they want to prevent deaths of his citizens, but Johnston and Jake disagree. They want to take out the mortars and go off with a team to do just that. They are successful, but Constantino radios Mayor Anderson to tell him there will be no more negotiations.
Johnston leads a heavily outnumbered army of citizens into battle against New Bern. Hawkins helps the men by using his satellite to track the movements of the New Bern troops.