S8, E9: Sam and Dean are at odds after Sam asks a hunter named Martin (guest star Jon Gries) to keep an eye on Benny without telling Dean. However, when Martin tells Sam that Benny, might be responsible for a string of vampire-drained bodies in a small Louisiana town, Dean defends his friend. When Martin decides to take things into his own hands, things get messy and Dean is forced to make a very hard decision.