Azazael, leader of the Demon Coven, has been experimenting with angelic grace. Two of his subjects escape and call on the archangel Gabriel to help. Anna brings Gabriel an infant born of both a human soul and pieces of Anna’s grace. She begs Gabriel to use the last of her Grace to save baby, Castiel. Gabe takes Castiel in after binding his unstable angelic Grace, knowing that only Cas’ soul compliment could ever make it possible for his angelic powers to be unbound.
Years later, Dean Winchester gets a desperate call from his witch-trainee brother, Sam. Sam thought he could handle a hunt with just his friend Cas’ help, but instead Sam only escaped the evil witch they were hunting because Cas saved him at the cost of his own freedom. Dean agrees to help Cas, thinking he will help his brother’s healer-witch friend and then chew Sam out for being an idiot. Instead, Dean finds himself up against the coven responsible for his mother’s death while also wrestling with the unexpected bond he shares with Castiel.