Anyway, I realized what was going on when I started watching at about the 25-minute mark. As you can imagine, I was confused for a while. I came in at the point where Sam and Dean are talking to a vampire on a bench drinking what looks like a Big Gulp. Evidently, something wonky is going on because the vamp doesn't act like a vamp. I find out later that Dick Roman and his Leviathan buddies are putting something in the vamps' food supply (??) that's making them dumb. Later Edgar the Leviathan reveals that they plan to take out the vamps, werewolves, shifters, basically anything that feeds on humans so all the humans are left for the Leviathans. Wow, I'll be so glad when the Leviathans are gone.
Anyway, after a little online research, I figure out that there are three things that Sam and Dean need to make a weapon to kill the Leviathans. Something from Castiel, something from Crowley, and blood from the Alpha vampire. There's also a girl named Emily who Sam and Dean are helping, evidently because she'd been kidnapped as a child by the Alpha. Only she's playing Sam and Dean, and she's really on the Alpha's side. Dean, being Dean, makes a smart-ass comment about Stockholm syndrome.
When the Alpha's henchmen grab Sam and Dean, the boys try to tell the Alpha what Dick and his crew are up to, but the Alpha insists he's on good terms with Dick. But you see a hint of question in his expression, so it's not a surprise when Edgar shows up and the Alpha brings up what the boys said. Fighting ensues, and the boys, who have managed to free themselves, cut off Edgar's head. The Alpha gives Sam and Dan a glass of his blood for their weapon and sends them on their way, but not before agreeing to let a little boy he has taken go with them.
Meanwhile, back at the motel, Bobby jumps into a cleaning lady's body, figures out the code to the safe that holds his flask (to which his spirit is evidently attached), and heads off to presumably kick Dick Roman's ass. You know, for killing him. When Sam and Dean return to find Bobby and the flask gone, they worry about where Bobby is and what he's going to do, but they have no idea where to look for him. They talk about being partway to being able to take down Roman, and how the plan rests with Crowley now. "What could go wrong?" Dean asks.
Cut to a scene where Dick is calling up Crowley into a devil's trap and telling him they need to talk.
Word is that someone on the good side is going to bite it in the season finale, and I'm afraid it's going to be Castiel. I really don't want to see him gone for good, but then I want him and Bobby back to the way they were. My favorite episodes are the ones where Sam, Dean, Castiel and Bobby were working and wisecracking together. I miss that.