Agnes has loved her Red Creek home, secluded from the outside world, worshipping her God as their town's strict laws and their Prophet commands--not knowing she is in a cult. Then, when her brother Ezekiel faces death without insulin from the Outside, Agnes decides to risk being a sinner to obtain it for him. The Prophet grows more dangerously zealous, prompting Agnes to take a risk on Outsider boy Danny to help her and Ezekiel escape. They do so, only to find the Outside world being ravaged by a virus--a virus with which Agnes forms a mysterious connection.