Backstory and Origin Reveal: The film opens in 1981 at the original Freddy Fazbear's Pizza. A young Charlotte Emily (daughter of co-founder Henry Emily) witnesses a mascot-suited employee (William Afton) luring a child away. She desperately pleads with nearby adults for help, but her cries are ignored. Charlotte pursues Afton into the backroom, where Afton fatally stabs her. Stumbling back onto the main stage, Charlotte collapses onto a trapdoor; her dying soul possesses the original attraction hidden below—The Marionette.
The Present-Day Plot and Possession Twist: Decades later, paranormal YouTuber group "Spectral Scoopers" (Lisa, Alex, Rob), led by a mystery figure named Michael Afton (William Afton's son), break into the abandoned 1980s pizzeria. The group is brutally picked off: Alex is torn apart by Mangle clinging to the ceiling, and Rob is drowned by small Marionette Dolls in the River Voyage ride. The Marionette attacks Lisa (Mckenna Grace), physically possessing her body to act as an agile human host capable of operating outside the pizzeria.
Meanwhile, Abby’s strict science teacher Mr. Berg (Wayne Knight) smashes her animatronic model project. The spirit of Chica manipulates Abby, offering to intimidate Mr. Berg if Abby helps free the animatronics from their physical confines. Abby agrees, leading to Mr. Berg's gruesome demise.
The Climax and Resolution: As Charlotte/Lisa commands the "Toy" animatronics to launch an attack during Fazfest, Mike, Vanessa, and Henry Emily unite to stop the massacre. Henry confronts the possessed Lisa, using the original music box to soothe Charlotte’s soul, while Mike and Vanessa protect Abby. Abby uses her empathetic bond to rally the original "Withered/Classic" animatronics to fight back against the sleeker Toy models. Charlotte’s spirit is suppressed long enough for Lisa to be freed from possession, temporarily halting the animatronic crusade.
Hidden Meaning & Sequels Setup: The ending reveals that Michael Afton manipulated the paranormal team to awaken the original animatronics and gather remnant energy. In a post-credits scene, the lingering spirit of Springtrap/William Afton twitches inside the flooded remains of the old facility, teasing his return and setting up the story for Five Nights at Freddy's 3.