Sam and Dean are still actively feuding, so much so that when Sam gets wind of a case involving straight-laced people who turn into cold-blooded killers, Dean decides to sit it out.
Sam suspects possession. When he gets to the town, his investigation turns up clues to their past including a visit from Henry Winchester and a companion named Josie Sands in 1958 under the guise of the Men of Letters.
Henry's disguise back in the day was as a preacher and his companion as a nun (unless it wasn't a disguise at all). The Mother? A Mother Superior of course!
Flip through the photos. Maybe Sam can find some inspiration in Henry's actions in the town that will give him an idea how to mend his broken relationship with Dean.