Sam finds a really, really old computer at the heart of the Lair O' Letters, and it's full of vacuum tubes and hamster wheels, or whatever the hell made those things run back in the day. Thinking that the computer will be able to pinpoint fallen angels and warn Castiel while he's on his off-screen adventures, he wants to get the computer running again but doesn't know how. Maybe it needs new hamsters. While investigating the ancient machinery, Dean knocks over a jar of magic goo without noticing it. By the time the Winchesters get Charlie over to the LOL to fix the computer, the goo has formed a gross cocoon against the wall. Dean cuts open the cocoon and out pops L. Frank Baum's daughter Dorothy. She sealed herself in that jar with the Wicked Witch from Oz 75 years ago. Yeah, Oz is a real place, Baum was a Man of Letters and his daughter was/is a hunter.
The Wicked Witch is loose in the LOL and causing all kinds of mayhem, even though the place is supposed to be warded against all evil. She's looking for a key that will open a portal back to Oz so she can loose her flying monkeys on an unsuspecting Earth. For real, you guys. And nobody's like, "Whoa, hey, Oz is some kind of real dimension like Hell or Purgatory or whatever? Is this some new crap we have to worry about?" Everybody's trying to figure out how to get rid of Elphaba, because she's apparently unkillable. Nobody thinks to try the demon knife or angel blade on her, or seal her up in the jar again, but instead chase after her with magical poppy powder. Unsurprisingly, Elphaba kills Charlie in no time at all. Even more unsurprisingly, Dean has Ezekiel bring her back to life and then lies very unconvincingly about it.
Elphaba possesses both Dean and Sam, who then try to kill Charlie and Dorothy with some painfully terrible acting. It's pretty stunning, actually. Dorothy finds the ruby slippers she got off that one Wicked Witch she did manage to kill and passes them off to Charlie. This is odd in itself, because weren't they silver in the books and not ruby? Anyway, Charlie takes the weaponized slippers and stabs Elphaba with them just in time to keep the witch from retrieving her evil monkeys. Is she dead, or did she escape back to Oz? Maybe they should have tried dropping a house on this one, too, just to make sure.
In the end, Dorothy takes Charlie with her to Oz to continue fighting the good fight, and to look for Toto, who hopefully hasn't been dead for the last 75 years. For most of the episode, Sam has been adamant that the LOL is their workplace, and not their home, but has a change of heart just in time to utter that iconic line... "There's no place like home." Lordy. Stay tuned for the full recap.
THEN! The Winchesters met a young lady named Charlie Bradbury, who helped them out a few times with her amazing computer skillz. Charlie thought she might become a hunter, which gave the brothers pause until they saw her amazing gun skillz. They extended to her an open invitation to the Lair O' Letters, which they'd once been told was the "safest place on earth," because it was "warded against any evil ever created." Why they would remind us of this and then completely ignore it later in the episode is a mystery that not even Charlie with any number of her amazing skillz could solve.
NOW! Or, according to the date on the screen, 1935. Everything's in black and white to make everything look extra old-fashioned. A man opens up the little puzzle box that the Men of Letters like to keep their secret keys in. It's like the kiddie version of the Lament Configuration. Majestic music plays as he and another man unlock the door to the LOL and make their way down to the darkened hub. They each sit down at what passed for a computer station back then and plug in something that could be a vacuum tube or a fancy pepper shaker. "Protocols complete!" announces the older of the two men. "James Haggerty," he introduces himself. "Peter Jenkins," says the one who looks like Doogie Howser. They shake hands and beam with pride over their accomplishment. Then they notice nothing seems to be happening. "Did we do everything right?" young Jenkins asks.
As if to answer his question, the lights come up all around the LOL. Machinery hums from elsewhere in the building. "It took three years to build this dump," Haggerty notes, his nose in the air. "Dump," Jenkins repeats, disbelieving. "This 'dump' is the last, true beacon of light in a world gone topsy-turvy! This 'dump' is the epicenter of the ultimate chess match between good and evil!"
It takes but six months for the shine to wear off. "What a dump," Jenkins sighs as he and Haggerty engage in a literal chess match. "You know, when I got this assignment, I thought there'd be, I dunno, excitement? Adventure?" Haggerty takes a hit off his flask and says, "There's nothing worse than adventure, my boy." The phone rings on the table beside them. Instead of a dial, it just has one big button with the MOL's secret symbol on it. Haggerty chastises somebody on the other end of the line for not knowing the correct password. "There's protocol here, young lady," he reminds her. He listens a little more, then appears to decide that they can forgo protocol this one time and invites her over. "Damn hunter," Haggerty grumbles, then elucidates when Jenkins looks puzzled: "Frank's kid." Jenkins is awestruck, because it seems this Frank person did something amazing for his daughter.