In 1693, Thackery Binx, a teenage farmer living in Salem, Massachusetts, discovers his little sister Emily has been spirited away by the three Sanderson sisters, Winifred, Mary and Sarah, who intend to regain their youth by sucking the lives out of children through their witchcraft. Sneaking in the witches’ cottage, Binx’s attempt to save Emily fails when the sisters transform him into an immortal black cat and absorb Emily’s life force, regaining their youth. An angry mob led by Binx’s parents capture the sisters and prepare to hang them, but Winifred’s spell book casts a spell which will resurrect the sisters on All Hallows’ Eve when a virgin lights their black-flamed candle. After the sisters die, Binx guards their cottage for the next three hundred years to prevent their return.
On October 31, 1993, teenager Max Dennison struggles to come to terms with moving from Los Angeles to Salem, although he quickly develops a crush on fellow student Allison. After his new shoes are stolen by bullies Jay and Ernie “Ice”, Max is further frustrated when he has to take his mischievous little sister Dani trick-or-treating where he is humiliated further by Jay and Ernie. Max and Dani meet Allison at her house, and when Dani strikes up interest in the Sandersons, the trio venture to their old cottage turned into an abandoned museum. Max lights the candle, resurrecting the witches, who try to take Dani prisoner only for Max to fool them by igniting the building’s sprinkler system. Binx appears, instructing Max to steal Winifred’s spellbook. Realizing they have been had, the Sandersons give chase.
Confronting the children and Binx in a graveyard, the witches cannot land their brooms due to hallowed ground so Winifred summons Billy Butcherson from the dead, her former lover whom she poisoned after learning he had an affair with Sarah. Billy unenthusiastically follows Winifred’s orders and pursues the children and Binx across town with the witches not far behind whilst they explore the modern world, during which their brooms are taken by trick-or-treaters. The children venture to the town hall Halloween party which Max’s parents Dave and Jenny are attending. The Sandersons crash the party but perform “I Put a Spell on You” and enchant the adults to dance until they die. The children lure the witches to the high school where they trap them in a kiln and incinerate them.
However, the witches are revived and return home in despair, realising they were only revived for Halloween night and unless they kill more children they will turn to dust by the sunrise. The witches also take Jay and Ernie prisoner when they insult them. At Max’s house, Max and Allison read the spellbook to find a possible spell to reverse Binx’s curse, only for an unseen light to fire from the book and alert the Sandersons to its location. The witches capture Dani, Binx and the spellbook and fly back to their cottage, Sarah using a siren-like song to hypnotise the children of Salem into approaching the house. Max and Allison rescue Dani and Binx and flee to the graveyard, Winifred going after them despite having victory in her hands. Billy appears but turns on Winifred to aid the children and Binx, defending Dani around Billy’s grave and using salt as a weapon against the witches. Winifred captures Dani, with Binx trying to save her but is mortally wounded by Winifred.
Max drinks Winifred’s potion and offers his life in exchange for Dani’s freedom. Winifred grabs him but Max fights back, knocking them to the ground. The sun begins to rise, Winifred panicking and attempts to absorb Max’s life force but realises she has stepped on hallowed ground and turns to stone, before the light of the morning sun destroys the witches once and for all. Billy returns to his grave and falls asleep, but Binx finally dies thanks to the broken curse. His ghost approaches Max, Allison and Dani and thanks them before Emily’s ghost appears and brother and sister reunite and walk off into the afterlife together. Later, adults are freed from their own dancing curse, and Jay and Ernie remain trapped in the sisters’ cottage with the spellbook looking about for its mistresses.