It's that second episode with a Latin title that I was talking about a few weeks ago, Jus In Bello... The "First Look" spoiler clips have just been posted to YouTube for everyone to see, and I'm like this: O.O
So it goes without saying that the rest of this post is full of spoilers, and so are the clips themselves... (So stop reading this now if you don't want to know before it airs.)
There's two clips. The first kinda sets up the second a little bit, but the second one actually has Latin in it. Oh, YUM!
One thing you should probably know about it beforehand though is that Sam and Dean are being held by the FBI at some jail somewhere on a bunch of charges including many, many counts of murder, fraud, breaking and entering, arson, grave desecration, and the list goes on and on... The main agent after them (you'll see him in the first clip) has been trying to catch them since half-way through last season, and he thinks they are extremely dangerous psychopaths... Well, he's half-right. :D