A dark figure chases a terrified teenage boy, Ronnie Strickland, through a field in Texas. When Ronnie trips and falls, the figure pulls out a wooden stake and plunges it through his chest. Scully's voice calls out, and when the figure turns, we see that it is Agent Mulder. Pulling open the teenager's mouth, Mulder shows Scully two sharp incisors, much like vampire fangs. Upon closer examination, Scully determines the fangs are, in fact, a set of fake plastic teeth. Mulder realizes he has made a most egregious error.
When the agents return to their offices, they agree to discuss the events that led up to the killing before they speak with Skinner (as they both face potential prison sentences). Scully recounts her story first. As the tale unfolds, Mulder and Scully examine slides of dead cattle, the victims of a series of exsanguinations in a small Texas town. Mulder reveals that a vacationer from New Jersey, Mr. Funt, met the same fate, and authorities located two small puncture marks on his neck. The agents fly to Texas, where they meet with Sheriff Hartwell, a handsome man who immediately catches Scully's attention. With Hartwell's permission, the agents examine the victim's body. Mulder notices that Funt's shoes are untied, but is unsure of the clue's meaning. While he and the sheriff stake out a local cemetery, Scully performs an autopsy on the corpse. Later that night, Scully and Mulder regroup at their motel to discuss their findings. Scully reveals that the victim was drugged with chloral hydrate, more commonly referred to as knockout drops. Scully believes someone doped Funt and then withdrew his blood using a syringe, perhaps emulating vampires seen in the movies. Mulder then reveals that there has been another victim. As a tired Scully sets out to perform yet another autopsy, Ronnie the Pizza Guy (the same teenager Mulder staked in the opening teaser) shows up with a delivery. Scully tells the teenager to deliver the pizza to Mulder as she heads for her car in the motel parking lot.
During the second autopsy, Scully realizes that both victims consumed pizza as their last meal. She races back to the motel, where she finds a drugged Mulder lying on the floor. The pizza guy springs into view, prompting Scully to fire several rounds. This concludes Scully's version of events that led up to the teenager's death. Mulder, however, disagrees with Scully's details, and tells his version of the story.
As Mulder's version unfolds, it becomes clear that he is painting himself in a good-natured light, while Scully is depicted as being suspicious of his every word. After examining slides of the dead cows, the agents fly to Texas, where Scully finds herself attracted to Sheriff Hartwell. In Mulder's version, however, Hartwell is affected with large buck teeth and a substantial loss of I.Q. The agents split up: Scully performs the first autopsy, while Mulder and Sheriff Hartwell stake out the cemetery. While surveilling the cemetery, Mulder begins pouring sunflower seeds on the ground, explaining that vampires are obsessive-compulsive. Should a vampire appear, it would have to pick up the seeds--just like it would have to untie shoelaces. The sheriff is dispatched to investigate a disturbance at an RV park. Mulder tags along. There, the pair discover the body of the second victim. Tired and frustrated, Mulder returns to the motel, where he regroups with Scully. He informs his partner of the need for a new autopsy, and after Scully leaves, he accepts the pizza delivery from Ronnie. Later, he finds himself in a drug-induced stupor. Ronnie enters the motel room, his fangs exposed, his eyes glowing red. Thinking quickly, Mulder manages to throw sunflower seeds onto the floor. Unable to resist the obsessive-compulsive disorder, Ronnie drops to his knees and begins picking them up. Scully finishes the second autopsy, and realizing Mulder is in danger, races to the motel. She draws her weapon and fires, striking Ronnie right in the chest. Though still in a drug-induced haze, Mulder gives chase, eventually staking Ronnie.
Back in the present, a coroner inadvertently reanimates Ronnie's corpse by removing the stake. Skinner informs the agents of the new development, and the pair fly back to Texas. There, the pair meet up with Sheriff Hartwell. As Scully and the sheriff stake out the cemetery, Mulder makes his way to the RV park, certain it contains Ronnie's resting place.
Sheriff Hartwell, it turns out, is a vampire. He drugs Scully's coffee, and she passes out. Meanwhile, Mulder discovers Ronnie's coffin inside an RV. Using handcuffs, he traps the vampire inside the box. When the vehicle is surrounded by the undead, Mulder uses two pizza breadsticks to form a cross. The vampires shrug off the cross and pull Mulder downward. The next morning, a groggy Scully finds an unconscious Mulder inside his rental car. Mulder awakens--only to discover that the RV lot is now completely empty. The agents recount their bizarre tale to Skinner... who can only stare back at them.