Garth (DJ Qualls), the occasional work colleague of Sam and Dean, is hospitalised after being struck by a car, leading to the estranged Winchester brothers reuniting at his bedside.
Garth drops a bombshell on the brothers: he's now a werewolf... and married (to a werewolf). He explains that he has been taken in by his wife's family, a group of pacifist, Christian werewolves living in peace and harmony with humankind.
Dean and Sam are sceptical, to say the least. Investigating the family church they come across clues that lead them to believe the family is actually a cult of Fenris worshippers, seeking to bring on Ragnarok.
Naturally, things don't go well...
Sharp Teeth is an odd one. For more than half the episode it appears as though nothing truly Supernatural-like is going to happen and it unfolds as a character piece about the werewolf family, Garth's involvement with them and Dean's discomfort around them.
It isn't really until the brothers do their due diligence and unearth the werewolf cult that you get an idea of where the episode is going. Ultimately, almost like The Thule Society in Everybody Hates Hitler, the cult feels like it could have been a bigger, multi-episode, arc villain and, earlier in the show's epic run, it could well have been.
Is this the end of Garth's character story? It will be interesting to see where he goes from here and if he crops up again in the lives of Sam and Dean, otherwise Sharp Teeth really was a missed opportunity to explore the conflict felt by a hunter who becomes a monster.
While not the first that this has happened to, Garth retained his humanity and appears to have his lycanthropy under control. I just wish this aspect, although touched on, had been probed more deeply in the script.