‘Undertone’ Review: This Low-Budget Horror Sensation Can’t Live Up to Its Clever Premise

Anyone looking for a way to make their mark in horror filmmaking should see “Undertone.” Ian Tuason’s directorial debut is an example of the creativity that helps the indie horror space maintain its reputation as the ultimate incubator for exciting new voices — and proof that a clever concept executed well can often beat out movies with much bigger budgets.

The film, which follows the co-host of an occult-themed podcast who gets more than she bargained for when she starts listening to a series of mysterious recordings, takes place entirely in one location. We only see a handful of actors (one main character only appears through voice recordings), and over half the film consists of a protagonist hunched over a laptop sifting through audio files.

It’s a movie that almost anyone could have assembled the resources to make. And it achieved the ultimate indie film fairy tale ending, selling to A24 after its Fantasia premiere and going on to screen at Sundance before hitting theaters in March. The film’s success is a testament to Tuason’s creativity and the horror world’s willingness to embrace ideas that come from anywhere.

If all of that sounds like an attempt to delay saying anything about the substance of the film, that’s because it is. Unfortunately, “Undertone” is far more interesting as a phenomenon than an actual movie. Tuason and company deserve to be commended for telling a narrative film on such a small scale, but the finished product fails to deliver a conclusion that’s scary enough to justify its lethargic, slow-burn format.

Within the film, “The Undertone” is a podcast hosted by occult believer Justin (Adam DiMarco) and skeptic Evy (Nina Kiri). Each episode sees them debating a new creepy recording sent to them by a viewer, with Evy trying her best to debunk Justin’s paranoia and Justin trying to convince her that strange things are lurking all around us. There’s certainly an audience for such a product, but it’s hard to focus too much on audio entertainment while trying to care for a dying parent. Evy’s mother (Michèle Duquet) is bedridden, nonverbal, and her daughter’s only human companionship. And while it often looks like nothing is happening behind her eyes, the old woman occasionally shows moments of terrifying lucidity.

Evy is already navigating an unsustainable level of loneliness and exhaustion when she and Justin embark on a new 10-part series of “The Undertone” episodes. It all begins as a discussion of hidden messages allegedly found playing nursery rhymes backwards, only to give way to something far more sinister. The hosts are sent a series of 10 recordings that may or may not contain secret messages about a mythical source of evil just waiting to pounce.

It’s hard to overstate how subtle these messages are, and Evy’s investigation largely consists of slowing down and reversing various bursts of static with the hope of finding a few cryptic syllables that might help her make sense of whatever syllables she finds in the next recording. The film deserves an enormous amount of credit for its sound design, which allows Tuason to turn recordings that would be incomprehensible in less capable hands into something that keeps audiences on the edge of their seats for two thirds of a movie.

“Undertone” ends up being a victim of its own competence, as the early scenes of Evy’s investigation are shot so well that you’re certain it’s building towards something big enough to make you forget that you just spent 75 minutes watching a podcast host go through post-production. The climax sadly doesn’t deliver anything on that level, leaving you with the sense that you’d be better off listening to a podcast summary of these recordings than watching them yourself.

“Undertone” seems destined to live on as a film school case study, a lesson to ambitious young artists that marketable ideas can be found at any budget level. Its legacy as an actual film is much less clear. But even so, the creativity with which Tuason approached it is enough to leave this critic excited to see what he does next.

Grade: C+

“Undertone” premiered at the 2025 Fantasia International Film Festival before screening at the 2026 Sundance Film Festival. A24 will release it in theaters on Friday, March 13.

Want to stay up to date on IndieWire’s film reviews and critical thoughts? Subscribe here to our newly launched newsletter, In Review by David Ehrlich, in which our Chief Film Critic and Head Reviews Editor rounds up the best new reviews and streaming picks along with some exclusive musings — all only available to subscribers.