First off, how weird was it that Sam and Dean got along for the whole episode? It was so surreal, like there was going to be a twist at the end and the whole thing would be a dream. Anyway, Dean thinks he's losing his mind because he keeps seeing Castiel everywhere he looks. Then it turns out he was't losing his mind and Castiel was actually trying to get in touch with him for real, because he's totally back on Earth again. Castiel has no memory of how he got out of Purgatory, though, so instead of more hugs, he gets Dean's wariness.
Meanwhile, Crowley is abducting people from all over the planet. It's only when Castiel returns that the Winchesters discover these people are all potential prophets. It's like a Buffy thing where there can only be one at a time, barring a stupid contrivance. Crowley also finds Kevin, despite Mama Tran's best efforts to keep her baby boy safe. Mama Tran, by the way, has healed up quite nicely from her demonic ordeal. She enlists the Winchesters in rescuing Kevin from Crowley's Warehouse O' Torture.
Castiel insists on helping out, even though he's not at full strength yet. He takes on Crowley by himself and defeats him with some angelic mojo, which includes making his eyes even bluer than usual and flapping his cool shadow-wings. Crowley manages to escape with half the Word of God and one of Kevin's fingers, but the Lord's Littlest Prophet is fairly lucky, all things considered. The Winchesters turn him over to Garth, who you'll recall is suddenly completely competent.
At the end, Dean is feeling like a failure for not getting Castiel out of Purgatory himself. Castiel reveals that the only reason Dean wasn't able to rescue him is that he didn't want to be rescued. He wanted to stay in P-Town, which in his case stands for "penance," because he felt pretty awful almost destroying Heaven and Earth. While he's in the middle of confessing this to Dean, he gets zapped back to Heaven to meet someone named Naomi. (The lovely Amanda Tapping.) She basically tells him to spy on the Winchesters and report back to her, after which she will wipe all memories of such reports. When Castiel returns for the second half of the conversation, we see that his absence was either so brief or so metaphysical that the Winchesters didn't even notice he was gone. Nor does Castiel realize what's going on. Sleeper agent angel, anyone? Stay tuned for the full recap.
The ads for this episode pretty much gave away most of the surprise. I mean, they were all, "Welcome back, Cass!" in the voice-over and everything. It's understandable they would want to promote the episode and Misha Collins is a draw for a lot of viewers, but they basically showed every bit of Castiel's return, up to and including his reunion with Dean. It lessened something that should have had more of an emotional impact. Still, it was a hell of a lot better than the Civil War between the Winchesters that we got last week.
THEN! Dean and Sam found the Lord's Littlest Prophet, Kevin Tran, who was more than a bit surprised to see them after a year's absence. Dean explained that he was in Purgatory and Sam... well, Sam hit a dog. Kevin had managed to escape from Crowley by using a spell in the Word of God tablet (chapter: Demons) that blasted a bunch of minions into oblivion. The Winchesters reunited Kevin with his mother, who showed off her mean right hook by punching Crowley. Crowley possessed her for a bit and ran off with the tablet. Kevin escaped with his addled mother, leaving the Winchesters baffled for several episodes. Dean met an adorable angel named Samandriel who wore a delightfully tragic Wiener Hut uniform. Dean had several flashbacks to his escape from Purgatory, particularly of the moment when he somehow lost his grip on the Lord's Grubbiest Angel.
NOW! We open on a preschool playground perched right next to a glimmering lake. It seems like kind of a terrible place to put a preschool playground. There isn't even a fence. Hopefully swimming lessons are part of the curriculum. Most of the kids run around and frolic and squeal, but one boy sits at a table, elbow-deep in poster paint. A young woman kneels down beside him. "It's finger painting, Aaron, not body painting," she gently chides him. She leads him to the restroom to get cleaned up. Just before she follows him inside, she casts a look behind her as if to make sure the tots are still on dry land and not belly up in the water like last week's goldfish. But no, it's simply to make sure we see her eyes turn demonically black. As she closes herself in the restroom with little Aaron, a bright light flashes behind the door. Dark clouds gather over the playground. A strong wind begins to blow. A small tornado chases the children away from their swing set. The restroom door bangs open, revealing that Aaron and his demonic teacher have vanished. Taking their place is the fiery title card.