Ch.1 ~ a Room for Two?

Upon a fight in the bunker between the Winchester brothers Sam and Dean, Castiel proposes the two split up for awhile to have well-needed time apart. Cas(s) does this so that he may get alone time with Dean by taking him out on a hunt, just the two of them while Sam does whatever Sam does. While Dean and Cas(s) are out hunting they discover... they are being followed. This is where our story begins.