After The Doctor made himself known to the infamous Winchesters and helped them out with the foreign danger invading the bunker, two very different lives collided. As they navigate their new-found friendship and their differences, Sam, Dean, Castiel and The Doctor rush to protect their worlds as an old evil resurfaces. Finding themselves overpowered, their only option is to leave the planet as they struggle to find a way to keep Earth safe for good. Now, a deadly job threatens to lead them astray from their mission, and each other. Old and new enemies rise to meet them. What will it take for them to keep the world free from danger...?