What is the measure of a great horror film? Is it how high it makes you jump out of your theater seat (as with John Carpenter’s Halloween) or how many sleepless nights it causes you long after seeing it (as with The Haunting)? Mama, the new Spanish-Canadian film from Executive Producer Guillermo del Toro, does well by both measures. It sparks its share of high-voltage screams, but also makes you hold your breath back at home when you open a closet door or turn a blind corner. While it is a shrewdly calculated cinematic thrill ride, its core subject pierces the human psyche as sharply as a knitting needle to the back of the neck. Mama is about maternal instinct and its ability to transcend time, death and logic. What makes the film all the more haunting is that, like del Toro’s masterful Pan’s Labyrinth, its aesthetic is rooted in the great traditions of Spanish surrealism.

It’s difficult to tell how much artistic influence an executive producer has on a film, but Mama bears del Toro’s visual stamp through and through. Creepy woods, giant moths and dark hallways abound. Even the computer-generated titular character has the same surreal, child-nightmare quality of the creatures in Pan’s Labyrinth. But, as co-writer and director, Andres Muschietti must be credited with the wise choice of keeping the human drama (rather than the horror film trappings) front and center, for this is what sends the film burrowing into our consciousness.

The far-fetched plot sets up a real-life dynamic between the female characters: Two young sisters (Victoria and Lilly) are driven off a cliff by their father, who has just killed their mother and several others in a shooting rampage. The three survive, and take refuge in an abandoned cabin in the woods. Just as he is about to shoot Victoria, father is whisked away and killed by a ghost, Mama, who ends up raising the girls over the next five years. Their long-searching Uncle Jeffrey finally finds the girls and takes custody of his now feral nieces. Jeffrey’s punk-band bass-player girlfriend Annabel (Zero Dark Thirty’s Jessica Chastain, barely recognizable in a black wig) becomes the girls’ unwilling surrogate mother. Problem is, where Victoria and Lilly go, so does Mama, and a deadly quadrangle of mother-daughter bonding ensues.

Men don’t last long in the estrogen-fueled crossfire. Mama quickly sidelines Jeffrey to recover in the hospital, leaving her and an at-first unwitting Annabel to vie for the girls’ love and loyalty. Chastain, a terrific actor in any genre, is heart-achingly believable in her transition from indifference to deep maternal love. Small details and gestures speak volumes: Her first physical contact with Victoria is a master-dog head pat. Later in the film she strokes Victoria’s hair with a tender intimacy.

Mama is more haunting when she is left off-screen to fester in our imaginations. One of the most brilliant scenes occurs fairly early in the film, when through a bedroom doorway we see Lilly playing tug-of-war with Mama, who is blocked from our view by a wall. The subsequent quick flashes of her tragic, Modigliani-style face do trigger some impressive seat levitations in the audience, but when the two moms battle it out for the girls in the film’s climax, we are left with the all-too-common disappointment of modern movie fantasies–hand-to-hand combat between flesh and blood heroes and computer-generated villains.

The haunting, deeply disturbing qualities of Mama will stay with you once the aftertaste of its near-fiasco ending subsides. It will never reach the classic status of The Haunting or Pan’s Labyrinth, but its very real, sometimes courageous exploration of mother-love transcends the horror-film genre, while still providing plenty of popcorn-tossing chills.