|The episode starts with a man named Stan, and his girlfriend Penny, flying through a dark thunderstorm in a small plane. Penny is visibly rattled, begging her boyfriend to land the plane and Stan tries to calm her down. She is anything but calm, however, after looking out the window and seeing something huge flying outside beside them. Stan, unfortunately, fails to see the terror and tells her to close her eyes in an effort to get a hold of herself. She does so, but just then something breaks into the cockpit and pulls Stan out. Penny screams as the plane pummels downward without a pilot.
We see Castiel exit Bobby's panic room, where Sam lies unconscious, and assures Dean that Sam's soul is there, albeit 'skinned' and in complete anguish from being in Hell for so long. After telling Dean he is unsure when Sam will awaken, Castiel tells Dean he should have just killed Sam instead, before disappearing into thin air. A moment later and we find Dean having a drink with Bobby upstairs. Dean is afraid Sam won't wake up and Bobby assures him he will. With newspaper clippings scattered around Bobby's desk, they start to talk about a plane crash in Oregon, where the pilot's body was found seventeen miles away from the crash site and his girlfriend vanished without a trace. Suddenly Sam stumbles into the room and hugs both Dean and Bobby. After the heartfelt 'reunion', Dean and Bobby soon find out that Sam doesn't remember anything after falling into the pit with Lucifer and Michael. He does, however, feel incredibly hungry.
After serving Sam a decent plate of food, Dean and Bobby go over what Sam remembers. Sam does not, in fact, remember the last year and a half, and grows suspicious when he tries to figure out how he escaped hell. He asks Dean, who tells him he made a deal with Death. Sam is shocked and Bobby is reluctant to believe that they've heard the last of Death yet, but Dean assures them both that everything is fine.
Dean and Bobby talk privately a moment later and Bobby confesses that he still has qualms about trusting Sam, especially since he was nearly killed by his soulless counterpart ten days ago. Dean tells him that they must not reveal the truth to Sam, about his escapades as a soulless hunter, since it might stress the mental wall Death had created to hold back his memories of Hell. Bobby warns Dean that sooner or later, Sam is going to find out the truth for himself, and it won't be pretty when he does. But he agrees not to speak a word.
Just as Bobby and Dean are leaving for the investigation in Oregon, planning on leaving Sam behind to rest, they are confronted by Sam himself, who insists on going with them. Bobby then tells them he's going to stay behind to work the phones for Rufus, raising Sam's suspicion, and leaves. Sam asks Dean what that was all about, and Dean tells him its just old age and liqueur.
As they drive into Oregon, Sam discovers that two additional girls have vanished in the area. He then turns to Dean and asks whether he even tried to live a normal life, after he'd gone to Hell. Dean replies, saying he tried with Lisa and Ben, but it just didn't work out, and raises the volume on his radio before Sam can comment.
Dean and Sam are talking to Penny's sister, who expresses her dismay over the fact that Penny didn't even want to go up in that plane, and only did it for her boyfriend Stan. Sam and Dean return to their motel room and Sam discovers that the first two girls that disappeared were faithful Christians, but Penny was not. After reading through Penny's diary, something Dean managed to steal from her girly pink room, Dean confirms the fact that Penny was a virgin.
After walking with her friends from school, Melissa waves them goodbye and starts off down a lonely street. She soon feels the presence of something huge up in the sky and tries to run away, only to trip as the unknown assailant descends upon her.
Sam and Dean talk to Melissa a day later in the hospital, who claims she was attacked by something that looked like a giant bat and passed out after it clawed her shoulder. When she woke up, her golden promise ring was missing. It is then that Dean asks, subtly, whether she is a virgin or not. The only reason she hasn't disappeared is because she is not.
After some research in the motel, Sam comes to the conclusion that the only known thing interested in virgins and gold is dragons, in which he finds difficulty believing that they exist. Based on all the craziness of the past year, Dean says that it's possible and calls Bobby for advice. He's also skeptical that they're real, but assures Dean he'll look into the matter.
Sam goes through his dad's journal, hoping to find any mention of dragons, but instead finds a recent entry on skin-walkers. He asks Dean whether they'd just taken a skin-walker hunt, but Dean is adamant that they haven't. It is then that Bobby calls, and gives Dean the address to a Dr. Visyak, an expert in medieval studies at San Francisco University.
Meanwhile, in the damp sewers underneath the city, the captured virgins scream as a dragon flies in, shapeshifting into its human form and dropping off a new cellmate. He harms her when she tries to resist, and tosses her into the cell with the others, welding the iron gate shut with a glowing heat that emanates from his hand.
Dean finally reaches Visyak's private home, and manages to get through the front door after he tells her Bobby sent him. Visyak tells him to kick Bobby in the groin for her the next time he sees him and that he'll have to ask Bobby if he wants any further explanation. Dean then asks about the dragon and Visyak explains that they haven't been around for over seven hundred years. She continues by saying that the only thing that can kill a dragon is a blade forged with dragon's blood, and very few are left in the world to begin with. She, however, has one in her basement, lodged into solid stone, waiting for a 'brave knight' to pull it free. Dean tries to yank it out, but fails continually. He then tells Visyak that he has another idea, but he knows she won't like it.
While Dean struggles to get the blade, Sam continues his research back at the motel. He runs into a dead end, trying to figure out where the dragon's are holed up, and calls Bobby for help. The two come to the conclusion that the closest thing to caves in the area are sewers. Sam then asks Bobby if he's doing alright. Bobby tells him everything is fine, and that the events of the past year and a half, nothing having to do with Sam he claims, have just taken a toll on him and Dean. He promptly hangs up when Sam tries to question him further.
Sam tries to summon Castiel with prayer a moment afterward. Castiel appears and asks Sam how he feels with his soul back in place, completely unaware that Dean and Bobby hadn't told Sam that yet. Sam pretends like he's known, however, and asks the angel for a little more detail, since his memory is kind of hazy.
Back at Visyak's home, Dean latches several explosives onto the stone detaining the blade he needs. Visyak is obstinate, but Dean continues, convincing her that they have no other option. They take cover behind a closed door and Dean blows up the stone with his detonator. He finds the stone blown to pieces, and is dismayed when he finds most of the sword in the same condition as well.
Dean returns to Sam with only half of the blade intact and Sam points out the dragon's lair on a map, based on the locations of the abductions nearby. As they set off to the dragon's lair, Dean notices something off with Sam and asks if something is wrong. Sam says it's nothing.
The two descend into the sewers and find a pile of stolen gold jewelry and an old journal surrounded with lit candles. They suddenly hear the cries of the captured virgins in the distance and promptly follow the sound to help. They find the young women locked up, who warn the two that their captor is coming back soon. Just then, the dragon attacks in his human form. A second dragon in human form joins in on the scuffle but is killed when Sam stabs it in the back with the piece from Visyak's sword. At the sight of its partners demise, the first dragon flies off and escapes.
At Bobby's place, Dean expresses his happiness over the gold he took from the sewers. Sam then tells him that he has been informed about his soulless self and tells Dean that he should have been told earlier. Dean asks Sam who told him and is hardly surprised when he finds that Castiel's near childish mind is to blame. Sam continues by saying that he wants to make everything right, to apologize to all those that he'd wronged, stating that it was still part of him that had wronged them- with or without a soul. He then asks Dean for the specifics, but Dean warns him of the effect that might have. Sam replies by stating that Dean would want the same thing if placed in that precarious situation. Bobby suddenly calls to them from another room. He's been studying and translating the journal found in the dragon's lair since they got back, even discovering that its pages are made with human skin. He tells them it describes a horrid realm of blood, bone and torture, where all of the monster's souls reside.
Meanwhile, the dragon that managed to escape meets with another one of its comrades at an undisclosed location somewhere in the woods. The dragon is reprimanded for having lost the gathered virgins, but is told by the other that luckily they have enough. They then proceed to open the backdoor of a van and retrieve one of the many virgins inside, dragging her to a cave nearby.
Bobby continues to explain to Sam and Dean that the book mentions a ghastly realm, better known as Purgatory, and that it is actually more of an instruction book than a storybook. It details how to open a gateway to Purgatory, but the page with the specific instructions is missing.
The dragons proceed to drag the virgin deeper into the cave until they reach the edge of a dark abyss. We then see that the dragon that had escaped holds the missing page from the instruction book and begins to chant the incantation scrawled upon it, summoning a great fire from within the dark pit. He then proceeds to cut his arm and let his blood drip down into the flames. Just as the virgin screams in terror and pleads for her life, they throw her off the edge and into the fire as the first dragon finishes his chant.
Bobby is sure the book is supposed to be used to summon something out of Purgatory, but exactly what that is, he doesn't know. He only has one name, repeated throughout the text: Mother of All.
A slender woman with glowing eyes emerges from the fiery pit, floating in mid-air. The dragons greet her and she expresses her displeasure at the fact that it took them so long to release her. She then continues by stating that they have a lot to do, and it's time to get started.
[Roll the Credits!]