Undeserving Of Your Sympathy

The Mark of Cain comes with a lot of unwanted baggage. Dean finds himself falling victim to nightmares of himself killing the only two people dear to his heart, his brother Sam and his angel Castiel, due to the Mark.
His nightmares repeat every night but no matter how hard he tries to stop them, he cannot stop them from happening. Castiel soon realizes that something is wrong with his friend and comes to his aid.
The hunter and the angel quickly learn that the nightmares only get better when they end up sleeping in the same bed and eventually it becomes a daily ritual to sleep side by side.