This next episode is Garth centric and wow, we have almost no other information about it.
Previously: Dean partnered with Crowley to find The First Blade (TFB), the only weapon that can kill Abaddon. They met Cain (of Cain and Abel) who founded the Knights of Hell and who later killed all of the Knights except Abaddon using TFB. The catch: TFB isn't really a blade it is a jawbone than can only be used by someone wearing the Mark of Cain. When Abaddon's demons track down Dean, Crowley and Cain, Dean fights them off while Cain calmly watches. After the fight Cain declares Dean worthy of the Mark of Cain. Dean takes the Mark of Cain even though Cain warns him it comes with consequences and when Cain calls him Dean will have to return and kill Cain.
In the Men of Letters bunker Cas is healing Sam. He notices that Sam still has some of Gadreel's Grace in his body. Cas tells Sam the Grace can be used in a spell to find Gadreel. Sam tells Cas to take as much as he needs to find the missing angel. Cas stops before he extracts all the grace, fearing he will kill Sam, even though Sam is willing to die to stop Gadreel.
At the end of the episode both Crowley and Cas are trying to convince Dean and Sam respectively to make up and work together, but neither brother is currently interested.
GARTH RETURNS - After finding out that Garth (guest star DJ Qualls) is in the hospital, Sam (Jared Padalecki) and Dean (Jensen Ackles) go to check on him. Still carrying the guilt over Kevin, Dean lays into Garth about disappearing and demands to know where he's been. Garth makes an excuse and then hightails it away from the guys. Confused as to why Garth would run from them, Sam and Dean do some investigating and are stunned by what they find. John Showalter directed the episode written by Adam Glass (912).
There has been no sneak peek that I can find. The CHCH promo may go up today or tomorrow. If it does, I'll post it.
EDITED: Here's the promo. http://youtu.be/1AcAL5N_4mQ
So, what we know. The “good news” Garth has apparently found a home and a family. The bad news they seem to eat organs, grow fangs and fur and Garth seems to think he is a werewolf.
I don't have a lot of speculation here. When we first got the title I was hoping for a glimpse of Garth's nemesis The Tooth Fairy, but instead we get werewolves. Unless Sam and Dean reconcile off screen, they still shouldn't be working together. I'm guessing either they both get the call about Garth, or one of them gets the call and tells the other and they both go to see Garth. Frankly, I'm open to any suggestions about where this will go, because I've got nothing. Garth acted as a conciliator between Sam and Dean previously in Southern Comfort, so perhaps he will work to start bringing them together. Or we may just get crazy hijinks about Garth the werewolf. I feel fairly confident in calling this a stand alone episode.
ETA: Eight promo pictures were released just later this afternoon. Nope, still got nothing.