Supernatural: "Temptation of the Demon"

Sam and Dean reunite with their old friend Bobby. As they track down clues to John's whereabouts they find out that a buddy from John's Marine days has been murdered in a strange fashion. Further investigation leads them to meet a woman who may have made a deal where she's getting more than she bargained for -- Did John's friend meet the same demise? Are Sam and Dean finally close to tracking down Mary's killer? Yellow-eyes rear his well-coiffed head, and nothing ever will be the same.