Jake's return to Jericho after a long absence coincides with a deadly explosion that catapults residents into chaos, as they wonder whether they are the only people left alive.

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.

Jake brings people together to gather information about what is happening outside Jericho.

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 to school, a power line that has fallen causes an accident on the playground when the power returns, and 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. Meanwhile, Jake is held at gunpoint.