In Witsyebsk, Belarus, a Nazi soldier arrives back at base. The guard steps away to light a cigarette... and something huge attacks him, throwing him through the window. The first soldier sounds the alarm. Inside, a group of Nazis finish their work transcribing work into a tome while the attacker continues his assault, ignoring gunfire. As the remaining soldiers prepare to fire, their commander, Eckhart, casts a spell of cloaking. The attacker bursts through the door and kills the soldiers while Eckhart finishes his spell and yells at the creature to tell its masters that it isn't finished. He then disappears in a burst of flame.
In Lebanon, KS, Sam and Dean drive to the coordinates that the Elder gave to them. A huge abandoned dam stands at the site, and they use the key to go inside. The brothers confirm that the place was the nerve center of the Men of Letters and that it was abandoned on short notice. They turn on the power and discover that the place is appointed with expensive furniture and furnished bedrooms. While Dean grabs a shower, Sam goes through the group's books. He figures that they might have something there that could help humanity.
In Wilkes-Barre, PA, rabbi Isaac Bass goes to the local library and tells the librarian that he had to duck his pursuer three times. He asks to see a manuscript from the Holtzinger Estate and the librarian grumbles that it isn't the first time Bass has asked to see it. Once he's alone, Bass removes a tome from the case and studies the writing with interest. He then tells the librarian that they have to protect the book before his pursuer finds it. The man insists that it's part of the special collection and will be kept safe.
As Bass leaves, a man named Torvald watches him from the shadows. Bass goes to a bar and makes a call, saying that he found it and that they need a number. Outside, Torvald watches Bass. Once the rabbi finishes making his call, he calls outside and invites his follower to come in. As everyone watches, Bass starts screaming about Nazis and then bursts into flame.
Two Weeks Later
Dean checks in with Kevin and Garth, and then goes to see Sam. Neither one of them have heard from Castiel, and Sam explains that he's been charting out the Letters' circle of hunters and allies. He's found a file on a European team, the Judah Initiative. They were rabbis that acted as saboteurs against the Nazis. One of them, Bass, died two weeks ago of spontaneous combustion. The brothers figures that it's a case and head out.
The Winchesters drive to Wilkes-Barre and talk to the librarian, and Sam claims that he's a fellow researcher. Meanwhile, Dean talks to two women at the bar, and they explain that Bass was always talking about Nazi necromancers. A man at the bar, Aaron, takes an interest in the conversation and smiles at Dean. The women explain that the fire seemed to attack Bass as if it were alive.
Sam opens the case that Bass was examining on the day he died and finds a book on birds.
Dean talks to Aaron and asks why he's been following him, since he noticed him earlier. Aaron claims that he thought they shared a moment earlier, and followed him to get a date. Dean quickly backs off and goes outside, and Sam calls to tell him that Bass was apparently into birdwatching. As he talks, he notices someone following him and warns Dean. Sam asks Dean for help and they agree to meet at the visitor's parking lot.
That night, Sam goes to the lot and Dean approaches Sam's pursuer. It's the huge man, who throws Dean out of the bushes. Sam grabs a knife and attacks him, but the blade simply sinks into the man's arm. As the man chokes Sam, Aaron steps out and tells the man to stop. He then explains that the "man" is his golem.
Aaron takes the Winchesters to his apartment and explains that Bass was his grandfather. He came there to investigate his grandfather's death and brought the golem with him. Aaron explains about the golem, which is shaped from clay and brought to life by rabbis to protect the Jewish people. Bass, the last surviving member of the Judah initiative, left it to Aaron. The golem speaks up, asking why they should know about the Initiative, and the golem accepts that they are a descendent of a Man of Letters.
As Torvald watches from outside, the brothers compare notes with Aaron and explain that they grew up in the Hunter culture. Aaron never had any experience with the supernatural and assumed that Bass was just making up stories. After Bass died, the golem was delivered to his apartment in a box. The golem complains that Aaron isn't a rabbi and doesn't follow the Jewish traditions, and Aaron tells him to shut up. It tells Aaron to take charge and keeps walking around the room, glaring out the windows. Aaron explains that Bass was trying to track down the Thule Society, Nazi necromancers, and all he knows is that they were a secret fraternity bent on world domination. The Judah Initiative was started to fight them, and the golem tells Aaron to find them so he can do his work. Aaron explains that his grandfather left him a weird number on his answering machine on the day he died, and Sam realizes that it's a call number for libraries. He figures that it relates to the book he found earlier.
The Winchesters, Aaron, and the golem break into the library and Sam figures that Bass switched manuscripts. While the others wait, Sam goes up to the proper section and finds the Nazi book in the birdwatching section. As he takes the book, Torvald shoots him with a dart and he starts to pass out. The Nazi necromancer steps out and thanks Sam for leading him there, and Sam kicks a cart into him and runs downstairs. Torvald shoots Aaron and he and Sam both collapse, dying, from the spell on the dart. Dean tells the golem that they're going to die if they don't get the necromancer. The golem goes upstairs and finds the necromancer, knocking him unconscious. He then drags Torvald downstairs and breaks his neck, ending the spell.
When Aaron wakes up in his car, he finds himself out in the woods. Sam and Dean are burying the necromancer's body, while the golem tells Aaron that the Winchesters saved his life. Once they finish, the brothers wonder if they should destroy the golem since it's clearly out of control. Meanwhile, when Aaron sees the brothers burn the Nazi's bodies, he figures that they're psychopaths.
The next day, the trio reads the book and realizes that it's the Red Ledger, which describes the magical experiments that the Nazis performed on their victims. The golem speaks up, saying how horrible the experiments were, and Sam realizes that he was there. It explains that he was built in a ghetto and tore the camp down, and the commandant burned the place down around him. Sam asks why it is telling Aaron to take charge and the golem says that Aaron would know if he consulted the pages. Aaron reluctantly explains that Bass gave him a book in Hebrew showing him how to control the golem. However, he drifted in high school and used the pages for rolling cigarettes. When Aaron asks the golem to tell him what he needs to know, the golem angrily says that it's not his place to teach the teacher.
Sam returns to reading the Red Ledger and determines that the Nazis were trying to magically reanimate the dead back to life. They succeeded and the last page shows a list of dead Thule members who were resurrected. A headshot will kill a reanimated body, but if it's not burned then it will reanimate again in twelve hours.
Eckhart, still a young man, drives to the library with his assistant. The security cameras are wiped and Eckhart confirms that Torvald's ghost is gone and his remains burned. Eckhart finds the dents that the golem left as well as traces of clay, and realizes what they're up against.
Dean calls Garth to have him perform research on the Thule Society, but he doesn't find anything. Sam has been doing research on how to stop a golem but the research is sketchy. Aaron overhears them talking and insists that they don't have the right to decide to shut it down. He insists that it's his responsibility but admits that he doesn't know how to handle it.
The Thule Society members break in and quickly capture them, and the golem storms in and kills one man. Eckhart steps in and magically takes control of the golem before it can attack him. He then removes the scroll from its mouth that animates it and wonders why Aaron didn't take possession of the creature. Eckhart explains that Aaron had to write his name on the scroll to take control of it, and then slaps Aaron to the ground. He then asks where the Red Ledger is while his men search the house for it. As Eckhart toys with the scroll, Dean spots a shotgun nearby and gestures to Aaron, who shakes his head in the negative. Sam keeps Eckhart talking and he promises that they'll suffer for Torvald's death.
A Thule soldier finds the Red Ledger and gives it to Eckhart, who is satisfied that their secrets are safe. Aaron hits Eckhart with a board and Sam and Dean jump the soldiers. The last man uses Aaron as shield long enough to get out, and Eckhart dares them to kill him, vowing that they will never wipe out the Thule Society even if they kill him. They shoot him dead and check with Aaron, who says that he's okay.
Later, Aaron and the Winchesters dispose of Eckhart's body and return to Aaron's house. They ask Aaron if they want him to dispose of the golem, but he figures that the Thule society is still out there somewhere. Aaron looks at the scroll and says that his grandfather left him something important to do, and then writes his name on the scroll and puts it back in the golem's mouth. It comes back to life and bows to Aaron in a gesture of respect as the grandson figures that he's now the Judah Initiative.
Back at the Letters' headquarters, Sam makes copies of the Red Ledger and Dean wonders if he's becoming a Man of Letters. He then gets Sam a drink and says that if he is, it's good.