Citizen Fang is the 9th episode of Season 8. It aired on December 5, 2012.
Sam asks a hunter named Martin to keep an eye on Benny without telling Dean. However, when Martin tells Sam there was a vampire kill and he thinks Benny is responsible, Dean defends his friend. When Martin decides to take matters into his own hands, things get messy, and Dean is forced to make a very difficult decision.
Benny is working a late night at a small Cajun diner in Carencro, Louisiana. After his coworker Elizabeth leaves, one of the customers asks him about her. Benny tells him that Elizabeth's like a little sister to him. Another customer asks for a refill on his coffee, and Benny obliges. He doesn't recognize him, but it is Martin Creaser: a hunter that Dean and Sam have worked with before.
Later, Benny closes the diner alone and walks home through the woods. Martin follows, but loses track of him for a moment and then hears a scream. He pulls out a machete and starts running, but trips and falls next to a dead body. It's the other customer from the diner, his neck torn open.
The next day Martin calls Sam, who tells him not to do anything about Benny yet. He then admits to Dean that he's had Martin tracking Benny for the last week, but Martin saw him kill someone and they need to take care of him. Dean is upset that Sam asked Martin, who was only recently released from an insane asylum, to go anywhere near a hunt, but agrees that they should look into it. They drive down to Carencro and meet Martin at his motel room. Martin tells them that Benny, going by the name Roy, has been working at a gumbo shack and seemed to be cleaned up until Martin found the dead customer. When Dean learns that Martin didn't actually see Benny kill anyone, he's reluctant to believe the worst of his friend. Dean leaves in the Impala after Sam gives him a few hours to investigate things on his own.
Martin wants to kill Benny anyways, but Sam denies him. He says that he can't believe Dean would trust a Vampire, and Sam tells him that it's not always easy to see things clearly. He remembers a moment with Amelia at their home in Kermit, Texas. They had just learned that her husband Don was still alive, and Sam had asked her what she planned to say to him. She'd been conflicted, so he had made a plea for their relationship, saying that he didn't want to give up on them. Amelia had seemed to agree before saying that she needed some time alone to clear her head.
Dean's first stop is the diner, where he meets Elizabeth. He orders a piece of pecan pie, but they're out, so he asks her where he can find Roy. She tells him that Roy has been parking his camper in a more remote spot for the last few days. Dean, flirting, gives her his phone number and asks her to call if Roy shows up. On his way to find Benny, he tries to call him, but Benny doesn't answer. Eventually, he comes upon Benny washing his bloody hands and, machete behind his back, asks Benny what's going on. Benny tells him that he's just buried the second victim of a rogue vampire named Desmond. Desmond wants Benny to join his new nest and give him credibility, but Benny has refused, so Desmond is killing messy in an attempt to attract hunters and force Benny's hand. Benny doesn't want to be driven out of his hometown of Carencro and away from his great-granddaughter Elizabeth, so he has to kill Desmond and worry about hunters later. Dean tells him to wait while he convinces Sam and Martin to go after Desmond, instead.
Back at Martin's motel, Dean tries unsuccessfully to convince Sam and Martin that Benny is innocent. Eventually, Martin knocks Dean unconscious with the butt of a knife. Sam isn't happy, but still leaves with the other hunter after handcuffing Dean. Martin remarks that his brother choosing a vampire over him must hurt, and Sam flashes back to the moment he met Don in a town bar. The other man had told him that because he loved Amelia, he would respect whatever decision she made about which of them she wanted to be with, and he expected Sam to do the same. Then he left after buying Sam a drink.
After Sam and Martin leave, Dean wakes up and picks the handcuffs restraining him. He then calls Benny to tell him to lay low and avoid Sam while he takes care of Desmond; however, Benny knows where Desmond is and won't let Dean go after him alone. He'll help Dean kill him.
Benny is gone from his campsite by the time Sam and Martin find it. Martin sees a picture on the ground: it is Benny and Elizabeth together. Suddenly, Sam gets a text message from Amelia asking him for help. He drops everything to get back to Kermit right away, getting in Martin's car and driving away without him.
Meanwhile, Dean and Benny infiltrate Desmond's hideout. The vampire catches Dean by surprise and breaks his syringe of dead man's blood. Just before he can bite Dean, Benny decapitates him. Afterwards, Dean tells Benny that he needs to go deep underground: it's only a matter of time before more hunters show up in Carencro. They head back to the diner so that Benny can see Elizabeth one last time, and then he thanks Dean for believing in him and leaves town.
Dean leaves, too, and calls Martin from the road to tell him that he and Benny killed the other vampire and that he shouldn't go after Benny. Martin says that he's already left town, and Dean tells him to find a new line of work before hanging up. Martin's lying, though, and his next call is to Benny using Elizabeth's phone. Benny tells him to leave Elizabeth alone, and Martin tells Benny that he has 45 minutes to get back to Carencro.
He rushes back to the diner to find Martin holding Elizabeth hostage. She's tied to a chair and he has a knife to her neck. Benny tells Martin that he didn't kill the people in Carencro, but Martin doesn't care. When he realizes that Elizabeth doesn't know who Benny really is, he cuts her neck so that Benny's fangs descend and reveals that he's a monster and her great-grandfather. Benny asks Martin what he wants, and he tells him that he wants his head. He puts his head down on the diner's counter and tells Elizabeth that he's sorry just before Martin raises his machete.
Meanwhile, Sam's been unable to reach Amelia since her distress text. As he drives to Kermit, he remembers the moment Amelia confronted him as he packed his bags. She'd asked him why he was giving up on them, and he'd told her that he was trying to do the right thing: Don deserved a chance. Later, Sam finally arrives in Kermit and goes straight to Amelia's house. He sneaks around the back, gun raised, but when he looks in the window he sees Don and Amelia together, happy. He's confused, but after going back to Martin's car seems to realize something.
Dean is still driving away from Carencro in the Impala when he gets a phone call from Elizabeth, who seems to be in shock. She reminds Dean that he told her to call if she saw Roy, and Dean asks her if Roy is there. She just tells him to come, and Dean makes a quick u-turn and races back to the diner. When he gets there, Elizabeth is covered in blood and sitting on the steps outside the diner. Silent, he hands her a towel, and she presses it against the wound on her neck. Then he goes inside, where he finds more blood and Martin's dead body on the ground with his neck torn open.
Later, Sam is at a bar in Kermit, and he pulls out his phone to call the number Amelia's text came from. When Dean answers, he's not surprised. He asks Dean when he changed Amelia's number in his phone, and Dean admits that he did it a while ago in case he needed to get Sam out of the way for a while. Sam asks him if the case is done, and Dean tells him that it is, but Martin died. Sam asks him if it was Benny, and when Dean tries to explain what happened, Sam hangs up on him. He stands up to leave the bar, and when he turns around, he sees Amelia walking towards him.