|A teenaged girl, Kristen, arrives at a bar and shows her fake ID. She meets with the young man she met earlier, Robert, and who promised to meet her there. They talk, and he expresses his admiration for the poetry she posted on line. Kristen reaches for her journal to read him a poem, and gets a paper cut. Robert turns away and then leaves to refrain himself from attacking her. Later, he comes back and warns Kristen that he shouldn't be there, and that they can't be together. He tells Kristen to run but she insists she can handle it. He shows her his fangs and Kristen says that she knew it. She starts to bare her throat, but instead he offers to show her his 'world'. He takes her to a deserted building and another vampire, Boris, leaps out. They both attack her.
Dean and Sam are working a case, but Dean calls Lisa to tell her that he'll be home soon. She tells him to get home and they cut off, and Sam arrives to tell Dean that seven girls have turned up dead. They meet with Kristen's father, who tells them that she was acting strange and figures she was into something. He sends them up to her room, and they discover that she was obsessed with vampires. They search the room and find her laptop, and Sam finds e-mail from an admirer that claims he's a vampire. They find his letter inviting her to meet at the Black Rose.
Robert and the other vampires intercept a shipment of blood from a blood drive, kill the guard, and hijack the cargo.
The next day, Samuel calls Sam and tells him what happened with the hijacking. They wonder why vampires are stealing blood when they already have victims, but don't come up with an answer. The brothers go to the Black Rose and spot several likely suspects. They split up to follow them, and a vampire tries to sneak behind Sam and attacks Sam. Sam cuts off its head with a single knife blow.
A Goth boy is hitting on a girl in an alleyway when Dean finds him. He realizes that the boy is pretending to be a vampire to get laid, and tells him to leave. As Dean walks off, Boris attacks him and feeds him some of his blood, while Sam watches but hesitates, staring in seeming fascination. He finally draws a knife and attacks the vampire, but it flees. Sam turns to Dean, whose mouth is covered in blood.
The brothers go back to the motel and Dean is overwhelmed by the noise and the bright lights. Dean plans to have Samuel kill him when he gets there so he doesn't transform into a monster, but then wonders why Sam isn't freaked out. When Sam says he is, Dean says that he can hear his heart and can tell he's calm. Dean goes to the bathroom and examines himself in the mirror, and spots the first signs of fangs growing in. Sam finally comes to investigate and discovers that Dean has slipped out the window.
Lisa wakes up in her bedroom and finds Dean standing over her. He thanks her for everything that she and Ben have done for him, and then moves away from her. When she asks what's wrong, Dean insists that he's going to die soon and his life is violent. She wants a better answer and he grabs her and shoves her up against the wall, hearing her heart beat, and then turns away as his fangs start to emerge. He quickly goes outside into the hallway, and Ben comes out. Dean shoves him away and then runs out before he can be overwhelmed by hunger.
Samuel arrives at the motel and warns Sam that Dean is a monster... and he's hungry. He prepares to do what is necessary, and they realize that Dean is there. He tells them that he went to say goodbye to Lisa, and admits it was a lousy idea. Samuel demands to know if he fed, and Dean admits that he didn't. He tells Samuel to finish him off, but Samuel tells him that there's a cure and he's there to save him.
Samuel reveals that he has his grandfather's journal, and it has an untested cure. He warns that it will work, but Dean can't feed on any human blood or he's gone for good. One of the ingredients is the blood of the Boris, the vampire who turned him. Dean prepares to go to the vampires' nest, stun his attacker with dead man's blood, and get back to them. He knows where they are, based on their smell. Samuel gives him a syringe of dead man's blood and wishes him luck. Once Dean leaves, Samuel reminds Sam that they talked about the cure months ago. Sam denies it, but Samuel wonders if Sam let his brother get infected so they could find the alpha vamp they're looking for. Sam turns it back on his grandfather, and says he's just relieved that they can fix it.
Dean goes to the vampires' nest and sneaks in. He comes face-to-face with Robert, who says that Boris told him to keep an eye out and welcomes Dean into the nest. He gets him stolen blood from the van and offers Dean some, but Dean claims that he killed people already. Robert warns that they don't kill people anymore, and wants to know what killing is like. Dean agrees to tell him later. As Robert takes Dean to see Boris, he explains that they are both recruiters now. They arrive in a central chamber where Boris is coaching vampires in how to attract victims by writing poetry. He then welcomes Dean and casually assures him that if Sam or any hunter find them, they'll easily kill them. He then explains that he's over 600 years old, and that he recruits vampire fans. Once they're brought in, Boris "converts" them and uses them to recruit even more. When Dean wonders who else is involved, Boris tells him that it's their father's idea. He promises to tell Dean eventually, and then offers him the private tour.
Boris takes Dean away, and dean tries to stab him with the syringe. He spills a drop of the blood, and Boris hears it, spins, and restrains Dean. There's a sudden high-pitched whine and Boris collapses along with all the women in the cages, some of them muttering, "Father." Dean finally goes down himself, and experiences a telepathic sending of young vampire twins and a bald African-American man approaching them. Dean wakes up and finds the vampires moving in. He runs for it, fighting his way out, and decapitates first Robert and then the female vampires.
Sam and Samuel arrive outside as Dean continues to hack his way through the vampires. Boris confronts him and warns that he hasn't stopped anything, and it's bigger than both of them. He then gestures Dean to come at him. A few minutes later, Samuel and Sam come in and find Dean, alive and standing over Boris' decapitated body.
Back at the motel, Samuel prepares the cure while Sam asks Dean what he saw in the nest. Dean can't answer him due to his growing hunger, and brings himself to drink the cure once it's ready. He vomits and then remembering everything that happened to him, including the fact that Sam stood by and watched as Boris fed him his blood.
The next morning, the Winchesters are preparing to leave and Sam asks Dean what he saw in the nest. Dean doesn't know much, but he does know that they have a psychic link with their alpha, and he's sending them telepathic messages to recruit vampires to build an army. There's worse: the vampires aren't scared of them anymore.
As they prepare to leave, Dean can't bring himself to leave a message on Lisa's answering machine. He tells Sam that he can always count on him, and Sam agrees...