A group of teenagers gather at their high school for Saturday detention, only to be trapped inside when the chemical plant in their small town explodes.

The group tends to their sick classmates, but they soon discover that the peculiar illness is more than meets the eye.

Grover fights to protect Mary. Diesel and Natalie share a secret. Barrett works to contact the outside world.

A new deadly threat turns the survivors against each other. Barrett suggests an unpopular way to gather more information on the freaks.

Lashawn is acting strangely, and the kids begin to suspect he might be infected. Zoe and Barrett strike an uneasy alliance.

Running low on resources, Violet and Zoe take on a dangerous mission. Zoe and Natalie address their past.

A potentially deadly trip into the fallout shelter puts one of the group in grave danger. Grover learns disturbing information about Barrett.

One of the group must venture outside to look for help. Diesel reassesses his relationship with Natalie.

The arrival of someone at the school may represent new hope for the group. Grover decides if he can trust Violet with his secret.

Things come to a head when a traitor is revealed. One of the group makes a sacrifice as more secrets about the explosion are brought to light.

LaShawn returns to the high school, followed by a group of people, who present a grave threat to the kids at the school.

With one member of the group in critical condition and time running out, Grover ventures out of the school and finds much more than just supplies.

The group struggles with their shocking new reality. Grover returns with a new group of survivors to Barrett’s dismay.

Everyone's suspicious of the newcomers, especially after weapons start to go missing. Ollie and Anka try to bribe everyone with an unusual plan to get out of the valley.

As suspicions amongst the survivors grow, one member of the group goes rogue. Grover unintentionally reveals a secret and Violet feels betrayed.

Shunned by the group, Grover and Barrett make a difficult decision. A storm prevents the group from escaping the school so they find an imaginative way to pass the time.

Barrett reveals shocking information to Grover that forever changes him. Violet must contend with new friends and new enemies.

The group must defend the school against a lethal new force. Anka and Violet must come to terms with each other in order to save their friends.

Barrett and Grover discover a disturbing conspiracy. Those trapped in the fallout shelter might have found an escape route.

The situation with the intruders reaches a boiling point. Violet puts herself in a dangerous position to save the others.