Shana wakes up one morning to discover her little sister sleepwalking-- but she cannot talk and cannot be woken up. And she is heading with inexorable determination to a destination that only she knows. Soon they are joined by a flock of sleepwalkers from across America, on the same mysterious journey. And like Shana, there are other "shepherds" who follow the flock to protect their friends and family on the road ahead. They discover an America convulsed...