Plot

Despite his devotion to his hometown of Salem (and its Halloween celebration), Hubie Dubois is a figure of mockery for kids and adults alike. But this year, something is going bump in the night, and it's up to Hubie to save Halloween.

Good-natured but eccentric community volunteer Hubie Dubois finds himself at the center of a real murder case on Halloween night. Despite his devotion to his hometown of Salem, Massachusetts (and its legendary Halloween celebration), Hubie is a figure of mockery for kids and adults alike.—yusufpiskin

Hubie Dubois (Adam Sandler) is a dimwitted delicatessen employee in Salem, Massachusetts who is ridiculed by almost the entire city, and is the butt of many practical jokes while his antics have annoyed police sergeant Steve Downey (Kevin James), police sergeant Blake (Kenan Thompson), and Father Dave (Michael Chiklis). Hubie spends his time during Halloween monitoring the city as the official Halloween Helper. Halloween is Hubie's favorite holiday since childhood. As a Hebrew he wasn't allowed to celebrate any other Christian holiday.

Violet Valentine (Julie Bowen), Hubie's love interest and Sgt. Downey's ex-wife (they have been divorced for 4 years). Pete Landolfa (Ray Liotta), a rude man who recently lost his father and is one of Hubie's tormentors. Hubie lives with his mother (June Squibb).

The day before Halloween, Hubie meets his strange new neighbor Walter Lambert (Steve Buscemi) (who believes himself to be a 459-year-old werewolf), and news spreads around town about Richie Hartman (Rob Schneider), a childhood friend of Hubie who is a convict with severe bladder issues who escaped from a mental institution to get his roommate back there before he gets into trouble. Richie is known to be a violent offender and Steve is concerned since he testified against Richie at trial. Steve investigates reports during Halloween day, about strange incidents, such as a pig being mauled at a farm. Meanwhile Violet tells Hubie that she saw a Lambert grave at the cemetery and Hubie checks it out. The grave is of Walter's father which states that Walter was born in 1661, and never died.

The next day is Halloween; Hubie is working as Halloween Monitor and investigates Walter's home after reports of strange noises. Hubie finds Lambert in the basement with evidence that suggests that Lambert is changing into a werewolf. Lambert runs away when he sees Hubie. Having reported this to the police, he is "recruited" by Downey as an "AUU" (auxiliary undercover unit). Hubie believes this assignment is genuine, although Steve hopes it will deter Hubie from bothering him. Steve tells Hubie to gather all his intel, make detailed logs and throw them in a garbage can in front of the town hall, which he claims is monitored. Tommy (Noah Schnapp), Violet's foster son goes to a Halloween party to meet Megan McNally (Paris Berelc), a girl who is Tommy's dream girl.

Hubie goes to the same Halloween party to monitor the activities. However, it soon turns sour as all the kids turn against Hubie's policing. Hubie is tricked into going into a corn maze following reports about a lost child. Hubie's young co-worker Mike (Karan Brar) follows hoping to scare Hubie. Hubie finds Mike and sees him getting pulled into the maze and then disappearing.

Meanwhile Tommy's foster sisters Cooky and Danielle are out looking for him, while Violet is working the night shift at a diner, as a waitress. Hubie comes in for soup at the diner. Violet is always nice to Hubie and says how she called home and none of her kids picked up. Hubie is also worried as he saw Tommy with Megan in the corn maze and had told them to go home. Tommy and Megan reach home, while Hubie finds the girls and drops them home too.

Hubie moves his attention to monitoring a drive-in cinema (he found the ticket to the drive-in at the spot where Mike was abducted). Hubie's old classmates Lester (Tim Meadows) and Mary Hennessey (Maya Rudolph) scare Hubie after false reports of suspicious activity in one of the cars at the drive-in (who turn out to be trick-or-treat kids driven by Mr. Hennessey to throw eggs at Hubie). He flees into the woods and finds Walter. Walter thinks he is turning into a werewolf and chases Hubie to a haunted house in a fun fair that is overseen by Chantal Taylor (China Anne McClain) (an elementary school teacher who owns a Siberian Husky named Buster).

Mr. and Mrs. Hennessey are kidnapped while they are driving back home, and Sgt. Downey is alerted. At the haunted house, Hubie sees a Siberian Husky, thinking it is Walter in his final form. The husky then runs into the haunted house and Hubie chases it inside. It is eventually shown that the husky is Miss Taylor's pet dog Buster. Pete Landolfa goes in to scare Hubie but is kidnapped in front of him.

Sgt. Downey arrives and suggests to Mayor Benson that they cancel Halloween (Mike, Pete, and the Hennessey's are all missing). Hubie thinks it is Walter, but then Blake calls Downey stating that Walter is at the police station with Richie who had turned themselves in, who also reveals that Walter's real name is Nick Hudson. Richie had escaped, bringing Walter back to the mental institution which they refer to as the werewolf treatment center. Downey, Benson, and Dave agree that Hubie is the kidnapper, thinking he is getting revenge on his bullies. He runs away and goes to a radio station.

DJ Aurora (Shaquille O'Neal) tells Hubie that someone calls a lot more than him always requesting a song for Hubie. They all think Sgt. Downey's ex-wife Violet Valentine is the caller, who used a prepaid burner phone. The burner phone when called is revealed to be in Hubie's house and he races there, hoping his mother is okay. It is revealed that Hubie's mother kidnapped Pete, Mike, and the Hennesseys as revenge for tormenting Hubie and plans to burn them alive. He rescues them just as the police, the news media, Nick, and Richie arrive. His mother then scolds Pete, Mike, and the Hennesseys for all the things they did to Hubie, and they also admitted that they were jealous of him for various reasons. Hubie's mother suddenly disappears upon using the Frankenstein trick.

One year later, Hubie is married to Violet, is the new Mayor of Salem, and his new foster kids are going trick or treating dressed like people he knows. Having earned respect from the locals, Hubie goes into town on his bicycle with Downey escorting him and prepares for the Halloween festivities.