Vampire Weekend is a Halloween episode of Castle.
On Halloween Eve, Richard Castle is getting ready for his Halloween party when Beckett calls. A teenager has been found with a stake in his heart in the cemetery. From the ceramic fangs in the victim's mouth, Castle meets up with fang master Dr. Barry Frank who identifies the victim as Crow and gives them his address.
At Crow's apartment, they find out that he was a graphic artist and was working on a new graphic novel. From Alma the landlady, they learn Crow had a fight with a black-haired girl, whose name they learn is Vixen and that she runs a vampire coven. The team looks up Vixen on the internet, during which Ryan reveals that he once dated a girl with a vampire fetish but broke it off when he refused to have sex in a coffin. Though they can't get an address for Vixen, the coven's website does mention an upcoming meeting, but only someone with a username can get the information, forcing Ryan to call up his ex-girlfriend, though he refuses to sleep with her in a coffin.
Vixen tells them Crow was writing a graphic novel with his new boyfriend Daemon which was based on Morlock, a psycho who thinks he's a vampire due to suffering from photosensitivity. Using the novel, they track down Morlock, but can make little sense of his "ramblings of spots and burying wicked boys".
They learn that Crow's real name is Matthew Freeman. They call his family, but neither his father Alan Freeman nor stepmother Janice Freeman can help. The daughter Rosie Freeman tells them to check his portfolio.
Ryan comes up with the drawings which are sent to the head psychiatrist Dr. Holloway. From him, they learn Crow's main subject was not Morlock, but a woman who he depicted as an angel. Daemon, whose real name is Jonas Westfall, a graduate in forensic anthropology, is found dead from a gunshot, but Beckett finds his thesis papers, where the sketch of a woman murdered 18 years ago is found. They conclude from Crow's drawings that he saw the murder of the woman when he was two.
At that same time, Alan had reported his wife Elizabeth missing. From Elizabeth's maiden name Dryden, the grave found by Castle in the cemetery, they believe Mathew confronted his father with the murder in front of her grave and was killed.
Bringing Alan back to the precinct, along with his lawyer, he confesses that he changed his name to protect Rosie and married Janice, Mathew's nanny, but insists he had nothing to do with wife's disappearance. He also admits that Matthew had been drawing his real mother's face since he was nine, but he didn't want to break Rosie's heart by telling that everything she had known as a lie; Castle retorts that if he was in his shoes, he would've told his daughter the truth. Beckett then produces Matthew's drawings and the image of Elizabeth's digitally reconstructed face, revealing that Matthew witnesses his mother's murder. She also produces the gun that killed both Elizabeth and Jonas, found in the Freemans' residence. Alan is at a loss for words, insisting that it's not possible.
Stepping outside the interrogation room, Janice asks how long are they going to hold her husband. Beckett assures her they are just trying to get to the truth. Castle then notices that Janice has spots on her dress and lead her to Morlock, who identifies her as a murderer. Beckett later informs Alan that Janice murdered Elizabeth so she could have him to herself. But when Matthew and Jonas came close to uncovering the truth, she killed Jonas and, spotting the stakes in his apartment, killed Matthew in a way that Alan would assume that the people he hated were responsible. With tears in his eyes, Alan asks why would Janice kill someone she raised. Beckett says that Matthew was a constant reminder of what she had done and when he turned on her, he was no longer her son. Alan is free to go and comforts a heartbroken Rosie.
In the subplot, Alexis and her friend Paige are taking care of an egg, Fegin, as a Home Science project. When they go to a senior party, Paige gets intoxicated and has to be carried home by Castle. Castle calls Paige's parents and as revenge, Paige 'kills' Fegin. Castle tells Alexis that no matter what she does, he will always be there for her. Even if she gets an F in science.
In another subplot, Beckett continuously asks Castle what got him into writing murder mysteries. Castle invents the tale of finding the body of his housekeeper's son washed up on the beach, and in return, Beckett scares him in front of his Halloween party with a light-up frog inside her coat.