Jessica Chastain in Mama
Universal Pictures

Anyone underestimating the power of short film was not in attendance at Manhattan’s Tribeca Cinema in December 2009 for the New York Horror Film Festival screening of Andy Muschietti’s Mamá. In fewer than three minutes, the Argentinean-born filmmaker terrified the audience with his visually economical tale of two young sisters relentlessly pursued by a malevolent spectre they call “Mom.” Director Guillermo Del Toro tells journalists gathered on the Mama set in October 2011 that he had a similar reaction upon watching Muschietti’s work.

“My reaction was I crapped my pants!”

Del Toro, 48, is best known as the director of visceral horror films like Mimic and Blade II, as well as imaginative fantasies like Pan’s Labyrinth and Hellboy II: The Golden Army. But the Mexican-born filmmaker is also a champion of younger directors, having shepherded the likes of Juan Antonio Bayona’s The Orphanage, Troy Nixey’s Don’t Be Afraid of the Dark, and Guillem Morales’s Julia’s Eyes to the screen in recent years.

Having honed his filmmaking skills directing hundreds of commercials before Mamá came to Del Toro’s attention, Muschietti is the latest artist to benefit from the older director’s patronage. With Del Toro’s assistance, Muschietti and his producer/older sister Barbara fleshed out the short into a feature-length screenplay, with Luther creator (and frequent Del Toro collaborator) Neil Cross also taking a pass on the script.

“I love producing first-time movies because you bring voices to a genre that a lot of people come into for a different reason; a genuine love for it,” Del Toro says. “So when you find someone like Andy, like [Juan Antonio] Bayona, like Troy Nixey, there’s a voice in there.”

Shot in Toronto during the fall of 2011, Mama stars Nikolaj Coster-Waldau (Game of Thrones) as Lucas, an illustrator who becomes the foster parent to Victoria (Megan Charpentier) and Lily (Isabelle Nélisse), his dead brother’s young children, who have recently been found after five years living feral in the forest. How they survived for so long is a mystery.

Reluctantly taking on the role of surrogate mother is Lucas’s girlfriend Annabelle (Jessica Chastain, Zero Dark Thirty), a bassist in a punk rock band. But the non-motherly Annabelle soon develops a bond with the girls – a bond that could threaten her very life when Mama, the supernatural entity that cared for Victoria and Lily all those years alone in the forest, makes her presence known.

“Annabelle is someone who never ever thought she would be around children,” Chastain says of her character, whose look was patterned after Alice Glass, frontwoman of Toronto electro duo Crystal Castles. “It’s not something she wants in her life at all, and she becomes the unwilling protector of these girls.

“It’s like Andy said to me in our first meeting. He said, ‘She becomes a hero of people.’”

The assembled journalists chuckle, and Del Toro adds: “It’s the syntax that gets you.”

Chastain’s decision to take on a horror film may surprise some. After all, the California native has become a critical darling in recent years thanks to highly-praised dramatic performances in movies like The Tree of Life, The Debt, and The Help, for which she received a Best Supporting Actress Oscar nomination. She is likewise receiving Oscar buzz for her role in Kathryn Bigelow’s Zero Dark Thirty, as the CIA operative who tracked down Osama Bin Laden.

“I was really surprised when it was first introduced to me, the script, because I thought, ‘I’m so not the expected choice,’” she admits. “And even that gave me more faith in, like, ‘Well, that’s really interesting, if you think I might bring something to this part.’ I’m also used to watching a lot of horror films where there is the girl in the tank top. I’m just not that idea of that.”

But for Chastain, who describes herself as “the biggest scaredy-cat ever,” doing a horror movie is exactly the sort of challenge she looks for when choosing roles.

“It has to be something where I think ‘I’m not sure I’ll be able to pull this off. We’ll see.’ Because when I have that feeling then it puts the element of horror and fear in me already, and I have to try to rise to the occasion. And I find with anything in my life, when you’re rising to the occasion, even if you don’t quite get there, you’re going beyond yourself somewhat.”

Chastain praises both Del Toro and the Muschiettis for making her initiation into the world of horror an easy one.

“It was so moving to meet them because family is really important to me,” she says. “And I just see a lot of sacrifices that they have both made, and they are a really good team that supports each other.”

“They’re like the dream brother and sister,” Del Toro adds. “My brother used to beat the s**t out of me!”

Mama opens across Canada January 18.