It's Christmas time in the clinic, but there's no occasion for joy when Sister Mary Augustine is brought, apparently suffering from stigmata. Figuring that it is nothing more than an allergy, House treats the nun accordingly--and as a result she nearly suffocates. As the other nuns set up a prayer vigil (much to House's annoyance), the clues to solving this medical mystery are painstakingly pieced together, leading unexpectedly to an incident in the Sister's distant past. Elsewhere, a man in a Santa suit (Dakin Matthews) is suffering from an inflamed bowel, which can only be cured by smoking cigarettes. Ho ho ho! ~ Hal Erickson, Rovi