After capturing Samandriel, Crowley broke into his "factory settings" with the help of demon torturer Viggo. Before the Winchesters and Castiel rescued Samandriel, Samandriel mentioned the existence of an angel tablet, leading to Naomi ordering his murder. Crowley then began a search for the angel tablet, somehow learning it was in one of Lucifer's Crypts and using Meg to locate them. Meanwhile, Naomi thoroughly brainwashes Castiel into her service and sends him on a hunt of his own for the angel tablet.
Searching for clues, Castiel discovers that Crowley has his demon possessing people in towns that Meg informs him that the Crypts are in as she claims not to know their exact location to buy herself time to escape. The places he hunts for the angel tablet are Benton, Indiana, Downers Grove, Illinois, Novi, Michigan and Lincoln Springs, Missouri. There, he captures and interrogates the demons Crowley has searching before killing them, but they don't know much about the search. The last demon he kills was possessing Ann Morton and had a meeting set up with Wendy Rice to find out what she knows about the location of an old orchard that had once existed in the town, but no longer did.
While looking for a case, the deaths of the possessed people draw Sam and Dean's attention as Castiel smote the demons which makes the deaths unusual. Investigating Ann Morton's death, Sam and Dean learn that she began acting strangely a week before her death, muttering about an orchard and digging holes all over the place then taking home dirt from the holes which she'd hang on a model of the town. When asked about any other weird behavior, Ann's husband tells them that when he went to confront her, she was talking on the phone and he noticed she had black eyes. He left to go to a bar and when he returned, she was dead. Sam and Dean realize that Ann was possessed by a demon and that so must've been all the other people killed, but they can't understand the demon's behavior. Checking on the other victims, Sam and Dean learn that they too displayed weird behavior and realize that they were possessed too but can't understand why they behaved as they did.
Looking for clues, Sam and Dean visit the house of Wendy Rice, the last person to speak to Ann in hopes of finding answers. Wendy explains that Ann had called her looking for an original map of the town as the town had been destroyed in a 100-year flood and then rebuilt. All of the original records of the town were destroyed in the flood, but Wendy was working on recreating a map of the town as part of her PhD dissertation. Ann had mentioned looking for an old orchard which Wendy had found the day before Sam and Dean visited her and shows them the location of on her map. Ann had never told Wendy why she was looking for the orchard as she was killed before they could meet, but Wendy tells them her assistant had called about the map and was on his way over and could possibly help them. Answering a knock at the door, Wendy is greeted by three demons, one of whom steals the map and flees. Dean fights another demon, but before he can kill it, it leaves its vessel and possesses Wendy instead and flees chased by Dean. The last demon attacks Sam who is unable to beat him. Suddenly, Castiel appears and smites the demon, having captured the possessed Wendy. Castiel then binds Wendy in a devil's trap for interrogation.
Sam and Dean question Castiel on where he's been and what he's doing. Castiel explains that he's been hunting demons and is the one killing the ones recently killed. When questioned on why he is hunting the demons, Castiel asks Naomi what he should tell the Winchesters and Naomi decides on most of the truth in hopes that Sam and Dean can get them closer to the angel tablet. Castiel tells the Winchesters that he has been hunting for the second half of the demon tablet and in the process discovered that Crowley has his demons searching for Lucifer's Crypts. While Castiel wants to tell the Winchesters the truth about why the demons are searching for the crypts, Naomi orders him to lie and Castiel claims that the demons are searching for a parchment that will allow them to decode Crowley's half of the demon tablet without a Prophet. The demons are possessing people who holds special knowledge about the history of the towns the crypts are in as the locations of the crypts were lost over time and only those closest to Lucifer knew where to find them. While Castiel doesn't know how Crowley knew where to start looking for the crypts, he decides to torture the demon possessing Wendy, hoping she knows more than the other demons he interrogated. Sam and Dean continue to notice Castiel's strange behavior, but don't have time to ponder it. The demon in Wendy briefly taunts Sam and Dean before Castiel starts using his angel blade to torture her for information on who gave the demons the location of the crypts. The demon refuses to tell him at first, but quickly breaks under Castiel's continued torture, telling them that they have a hostage who knows the location of the crypts, having seen them in the past. The demon tells them that hostage is located at the Murray Hotel down by the interstate. Dean asks if the hostage was who told the demons about the parchment they are supposedly looking for, but when the demon goes to tell the Winchesters the truth, Naomi orders Castiel to kill her. Castiel quickly stabs the demon with his angel blade, killing both the demon and Wendy Rice. Castiel tells the infuriated Winchesters that the demon gave them what they needed and he started the hunt without them so they wouldn't slow him down. Castiel then takes off for the Murray Hotel, leaving the Winchesters to race after him.
At the Murray Hotel, Castiel locates the demons room and engages them. Castiel quickly kills the two demons guarding the room just before Sam and Dean finally arrive, annoyed that he left them behind. Checking the bathroom, the Winchesters are shocked to find out that the demons hostage is Meg who disappeared after they defeated the Leviathans. The Winchesters realize that it was Meg who has been telling Crowley the location of the crypts which she confirms, explaining she knows their location as she visited them all with Azazel once. However, she gives them just enough information to get them in the general area of the crypts rather than telling them exactly where each is with enough having changed over time that the demons buy that she doesn't know their exact locations anymore. Meg gave them what she did in hopes of buying herself some time to find a way to get free and shows no remorse for her actions. The locations she's given the demons have all been false locations and Castiel keeps killing the demons Crowley sends to find them. As Meg prepares to tell the Winchesters what Crowley is really looking for, Castiel and Naomi discuss the situation and Castiel convinces Naomi that they can use Meg to find the crypts as Crowley was using her. Meg tells the Winchesters that Crowley is searching for the angel tablet and having found out that Lucifer had it, guessed that it was in one of his crypts which is why he's been searching for them. Castiel claims that the demons he interrogated must've lied about what they were looking for, but Dean doesn't buy it given how intense Castiel was when he tortured the demon possessing Wendy Rice. Meg points out that she lied about the local crypt's location so the demons are digging in the wrong place, but once they figure that out, they'll be back. Sam realizes Meg is right and asks for her help in finding the right crypt.
Returning to the Morton house, the Winchesters take Meg to the diorama Ann made of the town. Meg points out the correct location on the diorama, but is unable to tell them what's there now as none of the buildings were there when she had visited the crypt last. As Castiel treats Meg's wounds from the torture done to her and they flirt, Sam and Dean search for where the crypt's current location is and determine that it is beneath an abandoned building. As the Winchesters, Meg and Castiel take off for the crypt, the demon who escaped at Wendy Rice's house returns to the Murray Hotel to find the demon guards dead and Meg missing. He calls Crowley to report that he couldn't find the crypt at the location they were searching for using Ann and Wendy and that he's lost Meg. Angry, Crowley teleports to the hotel where he points out the demon's failures before killing him with an angel blade. Crowley then decides to go after the angel tablet himself.
At the building, Dean tells Sam to stay put outside and guard the building with Meg while he and Castiel search for the angel tablet. Sam protests, but Dean points out how Sam hasn't been fine since the First Trial as shown with him letting a demon get the better of him at Wendy Rice's house. While Sam continues to protest, Castiel tells him that its true and Sam is damaged in ways that even Castiel can't heal. He tells Sam to protect Meg while he and Dean go in since Meg is still weak from being tortured for over a year. Searching for the crypt, Castiel tells Dean that Sam is damaged on a subatomic level and he doesn't know if its lethal. He then locates a wall where there is a draft behind it and breaks down the wall to reveal the crypt. At the same time, as they put up demon warding on the building, Meg is angry that Sam and Dean never even searched for her after all the help she gave them defeating the Leviathans. Sam refuses to tell her about the Trials and what Castiel means about him being damaged and Meg asks him if he's really okay with dying since she knows he wants a normal life from the time she possessed him. Sam admits that he fell for a woman and left hunting for her which impresses Meg who gets him to talk about it. Rather than being disgusted, Meg indicates she knows what its like to fall in love with someone who changes you for the better.
In the crypt, Castiel spots the box holding the angel tablet as its the only thing warded against angels and alerts Naomi. She orders him to tell Dean the crypt is empty and come back later, but tells her there is no time for that as the demons are coming and the box is warded. Naomi tells him to handle it and Castiel points out the box to Dean who opens it and removes a block of stone inside which the angel tablet is sealed. Castiel asks for the tablet so he can take it to Heaven, but a suspicious Dean tells him they need to take it to Kevin instead for translation. Castiel tells him he'll take it to Kevin instead, but Dean refuses. Naomi, stating that if the demons get their hands on the angel tablet they can destroy Heaven, orders Castiel to kill Dean. Castiel tries to convince Dean to give him the tablet, but Dean tells him that he and Sam will take care of it and he can go back to searching for the second half of the demon tablet. As Dean asks Castiel for the truth about how he got out of Purgatory in exchange for the tablet, Naomi orders Castiel to kill Dean and he draws his angel blade to do so.
Under Naomi's control, Castiel attacks Dean who attempts to block with the angel tablet. Castiel tries to convince Naomi to stop, but she refuses, telling him that the tablet can do a lot for Heaven and they need it. She tells Castiel not to fight her control and to just let his vessel do what she claims he knows deep down is right. Castiel demands to know what Naomi did to him which Dean hears as he tries to talk Castiel down and asks who Naomi is. Naomi furiously tells him that there's blood everywhere and its on his hands and that she "fixed him." Eventually, when Dean puts his hand onto Castiel's shoulder to try to reach out to him, Castiel backhands him into a wall. As the two continue to fight, Castiel breaks Dean's arm, causing him to drop the block of stone, releasing the tablet. Castiel forces Dean to his knees and begins brutally beating him while Dean tells Castiel that he will have to kill him if he wants the angel tablet. Naomi orders Castiel to finish Dean and bring her the tablet and after brutally beating Dean's face to a pulp, Castiel raises his angel blade to kill him. However, Dean reaches out to him, telling him that they're family and Dean needs him. Naomi orders Castiel to choose a side and Castiel manages to regain control enough to drop his angel blade and pick up the angel tablet. The angel tablet glows and surrounds Castiel with power, breaking Naomi's hold on Castiel's mind and her connection to him, freeing him of her control.
Now having control of himself once more, Castiel heals Dean's injuries from his beating and apologizes, explaining what had happened to him and why he was acting so weird. Dean asks about what broke Naomi's control over him, but Castiel tells him that he doesn't know, he just knows that he needs to protect the angel tablet from both Naomi and Dean. As Dean asks what he means, Castiel disappears with the tablet. After Castiel leaves, Sam arrives and tells Dean they need to leave right away.
At the same time, two demons working for Crowley arrive and Sam and Meg engage them. Sam kills one with the demon-killing knife while Meg kills the other with an angel blade. However, Crowley himself shows up and is amused that they thought that their warding could keep him out. Sam tells him it will keep him out long enough for Dean and Castiel to escape with the angel tablet and Crowley is not pleased to hear that it was Castiel hunting his demons and is also pissed at Sam for killing his hellhound previously. Meg tells Sam to save Dean and Castiel while she holds off Crowley and he leaves. Crowley tries to convince Meg to betray the Winchesters, telling her their plan to lock the Gates of Hell forever with all demons inside- her included. Meg tells him that she doesn't care as long as he dies and he attacks her.
Meg and Crowley fight, but Meg is no match for Crowley, especially in her weakened condition and she loses. Crowley taunts Meg, telling her that he could beat on her for an eternity, but Meg remains defiant. As the two face off, Sam and Dean reach the Impala and look back before they leave. Defiant to the end, Meg tells Crowley that as Castiel is not in the back seat, the angel tablet is long gone. Meg then stabs Crowley in the shoulder with her angel blade, slightly injuring him. In response, Crowley stabs Meg in the abdomen with an angel blade of his own, killing her. The Winchesters take the opportunity to flee in the Impala while Crowley is busy.
After the Winchesters escape and Meg's death, Crowley enters the crypt where he encounters Naomi with whom he has a history. Naomi tells Crowley that Castiel isn't in the wind as he thinks but rather doing what he's supposed to be doing: protecting the angel tablet. Crowley offers to make a deal with Naomi, but she just vanishes into thin air to his annoyance as he usually does that.
Sam and Dean are left wondering what happened, guessing that touching the angel tablet must've reset Castiel to his "factory settings." Dean doesn't care as Castiel has run off with "a Heavenly WMD" and tells Sam he can't take anymore lies from anyone. Sam tells him that he just wanted everything to be okay even though Castiel told him that he's not. Dean promises to help him carry the burden of the Trials while Naomi and her angels continue to search for Castiel who continues to flee with the angel tablet.
- Despite learning of the Winchesters' long-term plans which are not beneficial to her, Meg stays true to her alliance with them, making her the most trustworthy demon ally the Winchesters have gained over the course of the show. This is ironic as she started out as their first true demon enemy.
- Meg and Sam briefly bond during their protecting the building, with Meg showing sympathy for Sam's situation and an understanding of him from possessing him. She indicates she even gets where he's coming from with letting love change you for the better.
- Meg flirts with Castiel who is shown to be at least somewhat receptive. With her last words to Sam before sacrificing herself to hold off Crowley, Meg indicates that she is in fact in love with Castiel, calling him "my unicorn". She had only minutes before referred to Amelia Richardson as Sam's unicorn when talking about how love had apparently changed them both.