Hubie Dubois, portrayed by Adam Sandler, is a somewhat slow-witted delicatessen worker living in the town of Salem, Massachusetts. Unfortunately for Hubie, he is often the focus of ridicule and the target of numerous practical jokes. His antics even frustrate local law enforcement, including Sergeant Steve Downey, played by Kevin James, and Father Dave, performed by Michael Chiklis. For Hubie, Halloween holds a special place in his heart, having been his favorite holiday since childhood. As a Hebrew, he never had the chance to celebrate any Christian holidays, and thus, he dedicates himself to serving as the town's official Halloween Helper.
Among Hubie's concerns are his love interest, Violet Valentine, who is portrayed by Julie Bowen and happens to be the ex-wife of Sergeant Downey, and Pete Landolfa, who is played by Ray Liotta — a rude man who has taken pleasure in tormenting Hubie. Hubie lives with his mother and leads a quiet life, but everything begins to change when he meets his eccentric new neighbor, Walter Lambert, brought to life by Steve Buscemi, who believes he is a 459-year-old werewolf.
As Halloween approaches, unsettling news circulates about Hubie's childhood friend Richie, portrayed by Rob Schneider, who escapes from a mental institution. Rumors fly about strange events occurring in town, including reports of a pig being mauled on a local farm. When Violet mentions seeing a Lambert grave in the cemetery, Hubie investigates and discovers Walter's father’s tombstone, indicating that Walter was indeed born in 1661.
On the day of Halloween, while monitoring the celebrations, Hubie investigates Walter's home after receiving reports of odd noises. Shockingly, he finds Walter in the basement, amid clues indicating that he might be transforming into a werewolf. As Hubie gets deeper into his investigation, he finds himself "recruited" by Sergeant Downey into an unofficial role, thinking he can contribute positively, while Downey hopes this will keep Hubie from bothering him.
With mounting pressures, including Tommy, Violet’s foster son, trying to join his crush at a Halloween party, Hubie’s surveillance efforts lead him into increasingly precarious and humorous situations, including a corn maze where he loses track of his young co-worker, Mike.
In a twist of fate, Hubie encounters his old schoolmates, Lester and Mary, who trick him under false pretenses by yelling for help. As he dives deeper into the unfolding chaos, strange happenings occur, including the sudden kidnapping of Violet’s family, prompting a frantic response from the police. As suspicion mounts against Hubie, he races to uncover the truth behind the night’s events.
While racing against time, Hubie discovers a shocking truth: his own mother has been behind the kidnappings, holding the tormentors accountable for their past mistreatment of her son. In a climactic turn of events, Hubie manages to rescue the captives just as authorities descend upon the scene.
Fast forward a year, Hubie's life has taken a turn for the better. He is now happily married to Violet and has become the Mayor of Salem, having gained respect and acceptance from the townspeople. With his new family in tow, Hubie prepares to celebrate Halloween once more, proving that sometimes, the underdog's triumph can lead to unexpected joy.
