Fred Figglehorn, Lucas Cruikshank arrives home screaming, and a troubling flashback unfolds. The day before, he attended a music class where he played Fur Elise and received praise from his favorite music teacher, Mrs. Felson, who has trouble hearing. The next day, he expects to see Mrs. Felson again, only to meet her replacement, Mr. Devlin, who is seen cleaning up and discarding a hearing aid, which makes Fred uneasy. On his way home with his best friend Bertha, he notices a girl named Talia following them. Feeling watched, he hurries home in a panic.
The following day at school, Devlin promotes a community called Join the World of Music, urging everyone to participate. Fred suspects Devlin intends to turn the whole town into vampires by pushing his lessons, and to his horror, many students sign up. That night, Fred spies on Devlin and sees him burying something, which fuels his fear that a body may be hidden nearby. After a conversation with Talia, she suddenly vanishes, and Fred starts to doubt whether she’s real, imagining her as a ghost in his house and even tumbling down the stairs in a panic.
A knock at the door reveals Kevin’s mom inviting Fred and his mom to a party. In that moment, Fred learns that Talia is Kevin’s sister, which adds to the strange web surrounding Devlin. The next day, Devlin appears on the doorstep to pick up Fred’s mom for a date, deepening Fred’s unease.
Determined to prove Devlin is a vampire, Fred enlists Bertha’s help. They spy on Devlin and Fred’s mom on their date, with Bertha posing as a waitress. When Devlin remarks that Bertha looks like one of his students, she covers by saying she’s her mother. Suspicions rise as Devlin orders a bloody steak, and Fred notices Devlin’s old music teacher’s jacket, intensifying his concerns. That night, Fred slips and falls after realizing Devlin might have seen him spying. A wrestling arena excursion with his dad leads to a tag-team showdown between Fred and Devlin, with Kevin joining in on the other side. Fred’s dad defeats Devlin, and Fred pins Kevin, seemingly sealing the victory. Just as the moment seems real, Fred wakes up, discovering it was all a dream.
The next day, Fred becomes enchanted by Devlin, and enters another vivid daydream. This time, he imagines a troubling, homoerotic fantasy in which Devlin appears to be kissing and feeding on his neck. Disturbed by these thoughts and the taboos they touch, Fred snaps out of it and seeks help from his alter ego, Derf. Derf lectures him on how to ward off vampires using a makeshift plan inspired by items from the internet and even a street sign. He warns that stealing street signs is illegal, so Fred improvises by visiting a Chinese restaurant to obtain garlic chicken “hold the chicken” as part of his anti-vampire strategy.
Armed with crucifixes and garlic sauce-filled squirt guns, Fred heads to the piano recital where Devlin is set to perform with his minion. He stages a so-called “Vampire Shooting Spree,” spraying garlic-scented solution on guests, including Talia. Afterward, Devlin invites Fred to his house for dinner to bury the hatchet. Fred streams the encounter on his phone to prove Devlin is a vampire. Inside Devlin’s house, a hidden butcher’s room behind a wall of meat and bones is discovered. Devlin surprises Fred with a knife and a ceremonial headpiece, and Fred accidentally drops his live video feed into a boiling pot. The video freezes on Devlin’s image, leading viewers to suspect vampirism, but Devlin explains his odd hobbies, and Fred begins to see him in a different light.
Back at school, everyone has seen the video and believes Devlin is a vampire. Fred rushes to Devlin’s house to apologize, but Devlin is too despondent to answer. When Devlin loses his job and announces he’s moving, Fred feels guilt and tries to reverse everyone’s beliefs by portraying himself as the vampire. Bertha and Talia lend a hand, with Talia revealing her dislike for her brother. Kevin and his friends confront Devlin’s house, seeking to rescue Talia. Devlin tells them vampires aren’t real, but Bertha interrupts with a bold claim: “Vampires are real, but it’s not Devlin. It’s him!” In a chaotic moment, Bertha’s intervention leads Kevin to stab Fred, who is sprayed with fake blood. Devlin witnesses Fred’s remorse and accepts the apology, revealing that he quit his job and sold his house of his own accord, yet still regards Fred as a true friend. In the final scene, as Fred’s mom and Devlin prepare for dinner and head out, Fred glimpses a reflection-free presence in the mirror, confirming that Devlin is indeed a vampire. He screams in terror as the film ends.
[Note: All first-time character references include actor attributions as links where applicable: [Lucas Cruikshank], [Seth Morris], [Daniella Monet], [Ariel Winter], [Jake Weary], [John Cena], [Irene Tsu], [Siobhan Fallon Hogan], and [Stephanie Courtney].]
