Jack, the son of Lucifer and a powerful Nephilim, roams the earth with no idea of who or what he is and what havoc he can wreck, causing no small amount of tension between monster hunters Sam and Dean Winchester, as the brothers try to figure out what to do with him. Their angelic ally, Castiel, is out of reach and their mother Mary is trapped in an apocalyptic world with Lucifer. The Winchesters must reunite their family, rescue Castiel, and save the world from Lucifer ... again.