n 1653 Salem, Reverend Traske banishes a young Winifred Sanderson after she defied church authority by refusing to marry John Pritchett. Rather than allow her sisters, Mary and Sarah, be taken from her, Winifred escapes with them to a nearby forbidden forest.

There they meet Mother Witch who gifts Winifred her magic book for her sixteenth birthday but explicitly warns the sisters against casting a spell known as the Magicae Maxima, which makes the user all powerful. Mother Witch also teaches the sisters to retain their youthfulness by killing children .

In 2022, twenty-nine years after the Sanderson sisters were resurrected by the Black Flame Candle, Salem teenagers Becca and Izzy prepare to celebrate both Halloween and Becca's sixteenth birthday but turn down a party invitation from their estranged friend, Cassie Traske.

Becca and Izzy visit a magic shop (formerly the Sanderson cottage) run by Gilbert, who gifts Becca a candle for their annual birthday ritual. The girls light the candle and discover that it is another Black Flame Candle. As there is a full moon and the girls are both virgins, the candle resurrects the Sanderson sisters once again.

The girls outwit the sisters in a local Walgreens and escape to the magic shop where they discover that Gilbert tricked them into reviving the witches, having seen them on Halloween in 1993 and been taught how to make the candle by Book.

The sisters catch up to the girls and see a campaign flyer belonging to Mayor Jefry Traske, Cassie's father and Reverend Traske's descendant. Winifred decides they will cast the Magicae Maxima spell to eliminate him and take revenge on Salem. The sisters trap Izzy and Becca in the basement and leave to hunt down Traske, whose blood is needed to complete the spell. They force Gilbert to collect the other ingredients.

The girls escape and head to the Traske house to warn the mayor while the sisters find their way to the town's Halloween carnival and enchant the citizens to help them find the mayor. Meanwhile, Gilbert digs up Billy Butcherson, who has been awake but entombed since 1993. He needs Billy's head for the spell but tricks him into helping him collect the other ingredients first.

The girls reunite with Cassie and trap the sisters within a salt circle in Cassie's garage before Mayor Traske returns home. The three teens make amends with one another but their reunion is interrupted when the sisters escape the circle and kidnap Cassie to use her blood instead. Becca and Izzy follow them to the forbidden forest where Gilbert has assembled the ingredients and soon discover that Becca is also a witch.

The sisters partially cast the spell and increase their power, but Becca distracts them while Izzy rescues Cassie. Becca convinces the Book that it does not have to answer to Winifred, and she and the Book flee further into the forest. The Book shows them a warning about the Magicae Maxima spell, stating that whoever casts it must give up what they cherish most.

The girls agree to warn Winifred of the price of the spell but are too late: she becomes all powerful as Mary and Sarah fade to dust. Winifred grows despondent and begs the teenagers to use their newfound powers to save her sisters. While they cannot save them, Becca, Cassie and Izzy join together in a coven and cast a reuniting spell so Winifred happily fades away to be reunited with her sisters.

Gilbert and Billy join the girls. Billy starts to fade away, realizing that all of Winifred's spells have be