At this point, Eve morphs up into Burnt Mary form -- just for shits and giggles, I suppose -- and while Samantha Smith certainly is far more entertaining to watch in the role than poor Julia Maxwell could ever hope to be, she's still stuck delivering this ungainly exposition dump for the audience's supposed benefit, so sorry, Burnt Mary, but I'm going to be skimming through your Talky Bits as well. "Kisses!"
Mother Mary insists she only wants Crowley dead -- for what he's done to her children, of course -- and when Dean snots back that the "little limey mook" in question "roasted months ago," Mother Mary's forced to reveal that Crowley actually still walks among us. Consternation abounds, of course, and then we get an even bigger exposition dump: The whole thing's about the souls. As you'll recall from the last couple of episodes, souls equal power for whomever happens to own them, and Crowley's apparently attempting to assume control of Purgatory in order to "siphon off" Mother Mary's supply of the things. Just go with it. And maybe think of this scene while you're doing so. You're welcome.
So, anyway, how has she decided to fight back? By turning every human being on the planet into one of her children (which, by the way, ties in to various monsters' claims earlier in the season about amassing armies, if anyone can remember that far back at this point). The experiments she's been conducting in Grants Pass -- the infectious but ultimately too-watery shapeshifters, the initial vampire-ghoul hybrids whose brains fried from the inside out, the ultimately successful Jefferson Starships -- were all geared towards that end. She needed a new sort of offspring that could inconspicuously propagate itself through an entire town's population in less than a day while also remaining shielded from your typical hunter's tests, and she succeeded. In fact, Sam and Dean have been tooling around with one of her new, improved creations all day -- Imminent Corpse One! Or maybe it was Imminent Corpse Two. I have no idea. "I'm bored!" How the hell do you think I feel, lizard?
Fortunately -- and almost as if it anticipated our desperate need at the moment -- the camera leaps over to Cave Junction or Wilderville or wherever to follow along as Soon-To-Be-Dead Uncle wanders into his living room to find...Imminent Corpse One, sprawled across the carpeting in a rapidly expanding pool of his own blood! "GOOOOOOOOOOOOORE!" Soon-To-Be-Dead Uncle spins around to dial 9-1-1, only to find his path blocked by...Imminent Corpse Two, whose mouth is coated with pieces of his brother's neck! "GOOOOOOOOOOOOORE!" And then Imminent Corpse One's menacing Soon-To-Be-Dead Uncle from the other side! "VIOLENCE!" The Imminent Corpses leap up to tackle Soon-To-Be-Dead Uncle to the floor, and as the camera discreetly pans away from the impending carnage to take in a tasteful set of family photographs on the mantel, a fresh gout of arterial spray erupts from Soon-To-Be-Dead Uncle's neck to paint this evening's next METAL TEETH CHOMP! red. "EEEEEEEEEEEEE!"