By Jeff Labrecque
Updated February 29, 2016 at 05:06 PM EST
Credit: MPI Media Group

There’s a proud tradition in scary movies that depicts the babysitter as the vulnerable target of some lunatic. But what if the babysitter is the lunatic?

In Emelie, Sarah Bolger (Once Upon a Time) plays the last-minute replacement to watch the three Thompson children. She seems normal enough — pretty and sweet. But as soon as Mom and Dad pull out of the driveway for their romantic date, the mood in the house begins to shift. Something is off about Anna, and while she lavishes attention on baby brother Christopher, older brother Jacob suspects that Anna isn’t exactly who she says she is.

“We allow housekeepers and babysitters and Uber drivers into our lives, handing over the keys to our home to a practical stranger — it’s become a normality,” says Bolger. “This is a real girl who enters a home and you’re letting a monster into your house unbeknownst to yourself. She’s kind of a backwards villain: You don’t know what her intentions are, so you can’t understand why she’s doing these things — like, who does she hate?”

As the evening progresses, conventional babysitter fun and games give way to warped activities that even the children recognize are wrong. But getting help isn’t easy. In this exclusive scene (above), the regular babysitter’s BFF comes to the door and is surprised to find Emelie there instead. In order to keep her cover, Emelie forces the children to the door to prove that everything is alright. When middle-child Sally tries to sound the alarm, however, she forces Emelie to improvise.

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“I love Jason Statham movies, like Transporter — he seems like someone who when he kicks you, you do not get back up,” says Bolger. “Emelie is not a fighter,​ but she is feral and she’s backed into a corner. That scene is her at her absolute most brutal: she whacks that girl three times — not once, like Jason Statham can do — she does it three times because she needs to ensure she never gets back up.”

Playing someone deranged was great fun for Bolger, but she and director Michael Thelin were careful not to traumatize the three child actors — a situation she appreciated from when she starred in In America as a 11 year old. The young actors were not present for Emelie‘s most terrifying scenes. “I was afraid to go too far and scare them,” she says. “I feel like Jim Sheridan probably did that for me and my sister when we were doing In America. You want everyone to feel as safe and happy as possible, and I wanted them to like me, too — and not be scared sh–less. Emelie’s gone through so much hardship in her past that she’s cracked. Whatever is inside of her is broken, and she’s sort of trying to fill this hole in her life in this very psychotic backwards way.”

Emelie opens on theater and VOD on March 4.