Guillermo del Toro presents: Mama

It could’ve been a classic.

Abandoned by their birth-father, Victoria and Lilly get supernatural assistance raising themselves in a cabin in the woods for five years before their uncle’s search party discovers them.

The child actors make sisters feel real, and Chastain and Coster-Waldau dazzle as their surrogate parents, Annabel and Jeffrey.

Chastain hints at warmth behind the disaffected rocker archetype, and her relationship with the two girls is the emotional heart of “Mama.”

Instead, it spends way too much time alternating between drawn-out exposition and forced scares. The film gets repetitive.

The film draws heavily from ghostly J-horror — “Mama’s” twisted maternal psychology, jerky body-horror, clicking vocal effects and cold color palette — but rarely unnerves as a creature feature.

“Mama” is at its best and scariest when it delves deep into the characters. As Annabel gradually accepts a maternal role, the film deftly interweaves dread-inducing scenes of dark humor and psychological horror.

Beautifully acted, the dread of “Mama” is lost somewhere in the telling.