Octavia Spencer stands between Anne Hathaway and a diabolical plan to transform children into mice in “The Witches,” an upcoming HBO Max pic. A trailer just dropped for the fantasy adventure.

Described as a “tough lady with a big heart,” Grandmother (Spencer) takes in Bruno, her grandson, following the tragic death of his parents. Little by little, she’s able to bring the child out of his sadness. But as Bruno warns, there’s “a dark shadow looming nearby” — and the pair are about to cross paths with its source.

Grandmother and Bruno find themselves at the same seaside resort as the Grand High Witch (Hathaway), who has developed a potion that turns children into mice. She and her kid-hating cronies are determined to rid the world of youngsters — and Bruno is one of their first targets.

“I well never let you get away with your filthy, evil plot,” Grandmother tells the Grand High Witch after she turns Bruno into a rodent.

As Grandmother emphasizes to Bruno, her love is unconditional. “It doesn’t matter who you are or what you look like as long as somebody loves you,” she tells her tiny, furry grandson.

Hathaway won an Oscar for “Les Misérables” and landed a nod for “Rachel Getting Married.” “The Last Thing He Wanted” and “Dark Waters” mark her most recent credits.

Spencer scored an Oscar for “The Help” and received nominations for “The Shape of Water” and “Hidden Figures.” She was last seen in her Emmy-nominated Netflix limited series “Self Made: Inspired by the Life of Madam C.J. Walker.”

Based on Roald Dahl’s novel of the same name, “The Witches” premieres on HBO Max just in time for Halloween, October 22.