Chanel, dressed in her Jackie Kennedy costume from the previous Halloween, is anguished over Chad's death. Denise, in a moment alone with Chad's body, expresses her own grief, reminisces about their romance, and vows to find his killer or die trying. She also vows to dress up as Mrs. Chad Radwell for Halloween, wearing Chanel's wedding dress.
Munsch and Denise visit Hester and ask her why the killer has changed their MO and is now killing people who are not CURE Institute patients. Hester suggests that they throw a party to lure out the killer but demands to be invited to the party. Denise and Munsch refuse and leave to go to Chad's will reading.
At the will reading, it is revealed that on the day he died, Chad's parents also died shortly before (in a plane crash en route to the wedding to change Chad's mind about marrying Chanel) leaving him the sole beneficiary. The lawyer also reveals that changed his will the day of his death, leaving all of his money to Dean Munsch and the CURE Institute "for reasons known only to her." In a rage, Chanel attacks the lawyer violently.
Because of her misery, Chanel decides to throw a "Chanel-o-ween" where she sends disgusting "gifts" from the morgue to all of her social media fans to let them all know how much she hates them all. As usual, the fans are deliriously happy to receive gifts from their idol, despite the fact that they're all blatantly cruel gifts.
Chanel goes to Dr. Holt about a viral infection rash that she's exhibiting. He hits on her and insinuates that he might be the killer, who Chanel thinks would be one mastermind leading a team of other killers and would have to be incredibly smart to pull that off. Holt prescribes Chanel silver to treat the viral infection.
The next morning, Chanel wakes up and is blue thanks to the silver she took. She flips out. #5 suggests that she can be Smurfette for Halloween, given her newly blue skin.
On the day before Halloween, Denise is in the hospital prepping for the party when she is attacked by the Green Meanie. She fights the killer off and tries to shoot them but they run away. Denise visits Hester and tells her that she's arranged to have Hester released for the night to go to the party, in exchange for Hester telling her who the killer is. She ill-advisedly gives Hester a Jason Voorhees costume to wear the whole night and an ax to go with it.
Chanel confronts Denise in the hospital, accusing Denise of having murdered Chad because Chad was going to marry Chanel. Denise denies that and tells her that Chad was never going to marry her -- he'd asked her to run away with him during one of their role-playing games, which may or may not have been the plot of the movie they were role-playing. Denise suggests that Munsch is behind the murder, along with Zayday Williams, given that Munsch inherited all of Chad's money. Chanel decides that they'll contact Chad via a spirit board to ask who he loved more and who killed him.
Chanel barges into Munsch's office and finds Holt canoodling with Dean Munsch on her chair. She demands that Holt be arrested for poisoning her with silver and probably killing Chad and others in cahoots with Denise Hemphill. Holt insists someone must have tampered with his medication suppy and promises to work on finding a cure for her supposedly incurable affliction. Munsch explains that Holt has an airtight alibi -- the two were having sex in her office right before Chanel and Chad's wedding. Chanel is horrified to hear that and insists that she's leaving the hospital. She storms out.
Chanel finds someone wearing an Ivanka Trump costume in one of the empty hospital rooms. The person attacks her violently, trying to kill her. Chanel narrowly escapes by throwing her shoe in the killer's face, but not before the killer stabs her in the leg. The killer lifts their mask after Chanel runs away tor reveal it is Hester.
While Zayday patches Chanel up from her wound, Chanel explains that her attacker was wearing an Ivanka Trump costume. Zayday and #3 gasp and reveal that they'd been helping #5 with her Ivanka Trump costume. #5 insists that it wasn't her who tried to kill Chanel, but they don't believe her -- especially when she can't locate the costume. Chanel declares that they're no longer friends and warns #5 that if she shows up to the party, they'll killer her.
At the Halloween party, Munsch dresses up as Hamilton, Zayday dresses up as Isis, Chanel as Smurfette, Cascade as Ryan Lochte, #3 as Death, and Holt as the script of Batman v. Superman (a "bloody mess"). They wait around hoping to draw the killer out. Someone in the same Ivanka costume shows up. They all assume it is #5 until #5 shows up in her Ivana Trump costume at the same time, having confused the two. As they all start freaking out over the killer not being #5, a horde of patients exhibiting psychosis pour into the hospital. The killer slips out.
The hospital staff rushes to figure out what's wrong with all of the patients. Holt believes that they're all suffering from Ergot poisoning from tainted apples while bobbing for apples. He prescribes a medicine that could be dangerous if he's misdiagnosed them, and Zayday disagrees with his diagnosis. Munsch agrees to give Zayday 10 minutes to figure out what else could be causing the patients' symptoms.
During the chaos, Chanel and Denise sneak off to summon Chad Radwell with the spirit board. Chad possesses Denise's body and tells Chanel to kill his goat Rammy for him and that he loved Denise more than her. He waits too long before telling Chanel who killed him and Zayday ends up interrupting, at which point Chad vanishes before he's able to tell them who the killer is.
In the hallway, Chanel #5 encounters Hester in the Ivanka costume. She mistakes Hester for Chanel in the costume and tries to talk Chanel down from killing her. Hester puts the knife down when she sees the Green Meanie sneak up behind #5. The unknown killer stabs #5 in the back, as Hester walks away calmly and doesn't help her.
Chanel, Zayday, and Denise interview the one person from the party who didn't get sick. The person who didn't get sick reveals that someone in a slimy green lizard costume swapped out the apple water. They test the water and find out it was poisoned with DMT -- a hallucinogenic molecule that is not deadly, meaning that Zayday was right and Holt was wrong.
Denise finds Chanel #5 bleeding but still alive in the abandoned part of the hospital. Before she can help her the Green Meanie appears and electrocutes Denise (apparently to death) using a defibrillator.