After being brought back to life by a mysterious force in the aftermath of the Miles County Massacre, Art the Clown sets off on a horrific rampage. He begins by gruesomely murdering a coroner who was examining his corpse, using a hammer in a brutal display of malice. Seeking to clean his blood-stained clothes, Art ventures into a laundromat, where he has a chilling encounter with a little girl clad in clown makeup, who only he can see. Unbeknownst to him, a lone bystander witnesses this unsettling interaction, but his fate is sealed when he is off-screen impaled through the head by a mop handle.
Fast forward a year, we meet Sienna Shaw, who is finalizing her Halloween costume—a fierce warrior princess conceived by her late father, who succumbed to a brain tumor. The loss has stirred troubling visions in her, while her younger brother, Jonathan, is determined to dress up as Art the Clown. Concerned for her brother's choice, Sienna confides in their mother, Barbara. That night, Sienna finds herself in a nightmare where she is confronted by Art during a bizarre restaurant commercial. In the dream, while the others receive candy, she is handed a heart in a box that oozes with worms and black goo. The chilling scene escalates as Art brandishes a Tommy gun, maliciously shooting everyone except Sienna, who desperately tries to escape. Her dream abruptly ends when a fire erupts from her dresser, destroying the wings she crafted, but her father's sword miraculously remains intact.
On Halloween day, Jonathan stumbles upon Art and the eerie little girl at school, playing with a deceased opossum. When he runs into a teacher, Jonathan is wrongfully suspended for allegedly bringing the animal to school. Meanwhile, Sienna heads to a costume shop for new wings, where she encounters Art again. He taunts her before committing an unspeakable act—mutilating the vendor and later viciously attacking Sienna's friend, Allie, at her home. Gruesomely pouring bleach onto her body and rubbing salt into her wounds, Art escalates his terror when Allie's mother discovers the grisly scene, only to meet her own fate at the hands of the clown, with her head grotesquely repurposed to serve candy to children.
As chaos unfolds, Barbara discovers Jonathan's suspension and forbids him from leaving the house. A heated argument ensues, and Jonathan storms out, only to later discover the harrowing aftermath of Art's attack—a mutilated and unrecognizable mother. Art follows and incapacitates Jonathan with a needle, leaving devastation in his wake.
At the party, Sienna unwittingly consumes molly given to her by Brooke. The combination of drugs leads to a panic attack when she sees the specter of the little girl clown. In the midst of the chaos, Jonathan manages to call out for help, but it’s the little girl impersonating his voice. This prompts Sienna's investigation into an abandoned carnival where she ventures into a haunted house named the Terrifier. As Sienna discovers Brooke’s lifeless body in a grimy restroom, she also finds Art and Jonathan. Time and again, she attempts to overcome the undead clown, but their struggle grows dire when she is stabbed in the stomach with her father’s sword, seemingly sealing her fate as she falls into yet another nightmare.
In the shadows, Art starts feasting on the comatose Jonathan. Meanwhile, Sienna is inexplicably revived through the power of her father’s sword and retaliates by beheading Art with it. Although he appears defeated, the ghastly little girl collects his head and vanishes as Sienna and Jonathan reunite in relief.
In a shocking post-credits twist, we find ourselves in a hospital where Victoria, the last surviving character from the previous film, is giving birth. In a disturbing turn of events, she scrawls profanities in blood on the walls as she brings Art’s head into the world. A horrified nurse stumbles upon the scene, screaming in horror at the nightmare that unfolds.
