Ian Tuason’s Undertone is a lean horror debut built on sound.

Nina Kiri as Evy Babic in *Undertone*. Photo by Dustin Rabin. Courtesy of A24

Undertone is writer-director Ian Tuason’s feature-length debut, a tightly controlled horror film built around the unsettling power of sound. Tuason initially gained recognition for his immersive live-action virtual reality horror shorts on YouTube, skills he brings to Undertone through its unnerving sound design and carefully controlled cinematography.

Nina Kiri, on-screen in nearly every shot, plays Evy Babic, a woman who has moved into her estranged mother’s house to care for her. As the story begins, Mama Babic (Michèle Duquet) is already comatose and has not eaten in days. Every other character is heard only from offscreen.

Michèle Duquet as Mama in *Undertone*. Photo by Dustin Rabin. Courtesy of A24

Evy is the skeptic half of a paranormal podcast duo. Her co-host, the true-believing Justin (Adam DiMarco), lives in London, which means Evy records their episodes at the naturally spooky hour of 3 a.m. from her mother’s dining room. When Justin receives a mysterious set of ten audio files from an anonymous source, the pair decide to build an episode around them. Over the next several days of recording, Evy becomes increasingly unsettled by the terrifying recordings as she struggles with the stress of caring for her mother and guilt over their strained relationship. The film was influenced by and written during Tuason’s experience caring for his parents at the end of their lives, and was shot in his childhood home.

The most impressive aspect of the film is its sound design, which is best experienced in a movie theater. The directional audio is always presented from Evy’s perspective, shifting dramatically as she puts on or removes her noise-canceling headphones. It creates a constant sense of dread and anticipation, especially as the boundary between the recordings and Evy’s reality begins to blur.

Nina Kiri as Evy Babic in *Undertone*. Courtesy of A24

While the audio does most of the heavy lifting, the cinematography is nearly as unsettling. Framing and lighting in the dark house often made me wonder if something was lurking just outside the frame. In several scenes, the camera slowly rotates in a full 360° pan, leaving me bracing for something to appear.

The performances are strong, both on-screen and off. It would be easy to overlook, but Michèle Duquet’s performance as Mama Babic is particularly notable. She never reacts to Evy, yet her unsettling presence forces both Evy and the audience to react to her. Her stillness and measured breathing feel disturbingly real.

Tuason’s film is an excellent example of how to create a compelling horror movie with limited resources. A single location, a small cast, and a meticulously designed soundscape combine into an exercise in creeping dread. I’m not sure how well Undertone would hold up outside a theater. At the very least, watch it with good headphones, or don’t bother.

Undertone opens in theaters on March 13.