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.