In Las Vegas, Nevada, a waitress, Kelly, is flirting with Dean at a strip bar. She points out that he came in looking unhappy and Dean explains about a "friend" with a younger brother who went nuts. His "friend" is worried that his brother has gone off on a hike into the desert. Kelly suggests that the younger brother might need some time alone. Dean gets a call from Sam from four blocks away, telling him to show up and wear a suit.
Dean arrives at a Vegas wedding chapel and notices the electricity flickering. He draws his gun and enters the main chapel... and finds Sam in a suit with a carnation. Sam hastily puts his brother's gun away, gets him up front, and pins a carnation on him. Dean figures that they're posing as wedding crashers, but Sam says that he's fallen in love and is getting married. Shocked, Dean starts to demand an explanation, but the music starts up and the bride-to-be comes in: Supernatural super-fan Becky Rosen.
Dean demands an explanation and Sam says that he ran into Becky, they talked, and he fell in love. Becky is well aware of Sam's history of ill-fated romance and figures she's going into the marriage with open eyes. Sam has confirmed that Becky is who she is supposed to be. The minister brings over the bill and Becky goes to pay for it, and Dean demands to know what Sam is thinking of. He suggests that Chuck might have written a new story saying that Sam would be in Las Vegas, but Sam says that he and his wife are heading to her home in Delaware while Dean wraps his mind around the idea of a married brother.
Dean calls Bobby and breaks the news to him, and says that he's going to Delaware to check things out. Meanwhile, Becky and Sam arrive in Pike Creek, Delaware, and Becky stops at a hotel to register with Jocelyn Caruso, the woman in charge of their high school 10-year-reunion. She shows off her new husband, and then heads outside. She runs into an old friend, Guy the event planner, and introduces him to Sam. Guy congratulates them and secretly slips Becky a vial of purple liquid, and she thanks him saying it helps to have a Wiccan as a friend.
Dean arrives at the hotel and settles down at the bar, and notices a newspaper article about a lottery winner who was killed when he was hit by a truck.
That night at Becky's home, they have dinner together and share a toast. Sam suddenly has a headache and wonders why he's there. Becky leaps into his lap and kisses him, and pours the vial contents into his drink. She has him drink it and he remembers her and their marriage again.
The next day at the local baseball stadium, a batter practices with a pitching machine while another man, Jackson, watches from the stands. The observer gestures, turning up the speed on the pitching machine, and then directs it at the batter, killing him.
Dean goes to Becky's place and offers a nonstick waffle iron as a wedding gift. Sam invites him in and Dean explains that he's working a case of two people that had extraordinary luck and then died a week later. Becky says that they already know about it and are looking into the matter, and Dean is shocked to learn that husband and wife are working the case together. He tells Becky that he knows she's up to something and will figure out what's going on, but Sam refuses to accept that something could be going on. Dean figures that since Becky is having her dream, she could end up dead just like the others. As Dean goes, Sam says that the fact that he's moving on with his life is what is bugging Dean, and now he doesn't need him. Dean glares at him for a moment and then leaves without a word.
Outside, Dean calls Bobby for backup, and Bobby directs him to another hunter.
In her room, Becky is writing Sam's name repeatedly in her diary. He comes in and gives her a present, fake his-and-hers IDs, and shows her a newspaper article about a new lucky person. As she reads the newspaper article, Sam finds her journal and says that it's beautiful.
Dean goes back to the hotel bar to meet with the hunter Bobby has sent his way. He finally finds the man, Garth. Garth explains that Bobby warned him that Dean would be all surly about having a new partner, and then takes the time to read the comics.
Garth and Dean go to check out the CEO, Craig Burrows, and discover that Sam and Becky are already there. Sam tells his brother that they made sure Craig was clear and that Becky handled it like a pro. Dean and Garth interview Craig anyway, and he says that the board just picked him out of the blue. When the man gets suspicious, Garth tells him that they're checking out the possibility of black magic. Dean shushes him and tries to get the interview back on track, and Craig says that he didn't want the job. His wife Marsha comes in, complaining about his assistant, and tells her husband to meet him later for supper. Craig admits that he's never seen Marsha happier, and that he's not sure how he'll tell her that he's going to resign. Dean and Garth go off after Marsha and try to warn her, but she denies everything and threatens to call security.
Sam is going over the case files when he gets another headache. Betty prepares to give him another dose of the serum from the vial, but discovers that it's leaked out of the vial.
As Marsha makes a call in the office lobby, Jackson is nearby and magically causes a decoration to fall on her. Dean arrives just in time to save her. She finally admits that a guy heard her complaining and made her an offer of Craig's job for her soul. Garth points out that demon deals are 10-year contracts and this situation has the deaths coming too fast. He suggests that they hide Marsha at his cousin's and find Sam.
Sam starts to snap out of Becky's spell and goes to call Dean, and Becky knocks him out with Dean's waffle iron. When he wakes up, Sam discovers that Becky has tied him to a bed at her parents' cabin. He demands that she release him, but she gets a call from Guy on her laptop. Becky asks for more elixir, pointing out that it's wearing off faster and faster, and admits that they haven't consummated their marriage yet. Guy tells her to meet him in an hour. When she goes back, Sam points out that he's overheard her through the walls and now knows that she dosed him. He tries to warn her about Guy, saying that he's her dealer, but Becky insists that Guy gave it to her for free and that the elixir only brings out feelings buried deep down. When Sam asks her to free him if she really loves him, Becky gags him and leaves.
Becky meets Guy where he's setting up the reunion. He tells her that they're past the freebie stage and now it's time to talk price. When she's surprised that he would charge, Guy tells her that she's pathetic yet cute and says that he will give her the elixir in return for her soul. He reveals that he's a crossroads demon, and Becky realizes that Sam was right. Guy assures her that she won't have an "accident," and offers her 25 years of happiness in her return for her promise of silence. Becky considers and then accepts.
Dean and Garth go back to Becky's apartment but find no sign of her or Sam. Garth checks her twitters and confirms that she was going on a trip with her husband. Dean finds a photo of her parents' cabin with the location written on the back and figures that's where she's holed up.
Becky returns to the cabin and tells Sam that she had hoped to show him off at the reunion. She talks about how didn't have a life until she met the real Sam and Dean. However, Chuck has dumped her and Becky wants someone to love her for who she really is. When she ungags Sam, he suggests that she shouldn't drug people if she wants them to love her. Becky takes out the vial and considers it, and am insists that she's better than that.
Becky goes back to see Guy after the reunion is over and tells him that she's in. He prepares to seal the deal with a kiss, but she use a lighter to ignite a pentagram that she drew in the carpet with blueberry vodka. Dean, Sam, and Garth arrive and demand an explanation. The demon finally explains that he has his "intern," Jackson, kill off his "clients" and collect early. Jackson shows up and knocks the three hunters back, and then breaks the pentagram. Dean tries to exorcise Guy's demon while the witch chokes Sam. However, Becky grabs the demon-killing knife and kills Jackson, and Sam tosses it to Dean. He puts the knife to Guy's throat and demands that he break the deals.
Crowley arrives and explains that he knows exactly what Guy has been up to, thanks to Jackson. He tells guy that the one rule that they have is that they don't break deals. If word gets out that Guy had found a loophole, no one would deal with them. He tells Sam and Dean that he'll cancel all the deals and make an example of Guy. When the brothers wonder why he's being so generous, Crowley explains that he's been keeping his demons away from the brothers and wishes them well in killing the Leviathans. They turn Guy over and Crowley teleports away with him.
Later, Sam signs the annulment papers and Becky asks if it was all bad. He admits that she did save his life but says that he won't be seeing her again. Becky signs the papers and Sam tells her that she's not a loser and to do her thing, and that the right guy will find her. He notices Garth looking at her, and Becky notices Garth looking at her, and Dean realizes that it's not going to end well.
As the brothers leave, Dean tells Garth that he doesn't suck, and the hunter admits it's the nicest thing that anyone has ever said to him. He hugs Dean for an uncomfortably long time and then departs. Sam apologizes to Dean for what he said and admits that he needs Dean to watch his back. Dean accepts his apology and Sam admits that he's still messed up, but at least he knows his way around. However, he points out that now Dean doesn't need to take care of him and can have some time to himself. Dean appears less than happy at the idea.