Buoyed by an excellent lead performance, Frida Kempff’s psychological horror is harrowing, but ill-served by a weak ending.

Sure, living in an apartment means you don’t have to worry about mortgages, property taxes or paying for new furnaces, but it also means trading in your privacy, and often being too aware of what your neighbors are doing. My upstairs neighbors seem to have either a small child or a large dog that runs back and forth across the living room floor, although I have not seen visual evidence of either. That’s an improvement over another neighbor, who I could hear cough and burp at all hours, and a third neighbor whose hobby was playing an electronic keyboard off-key. You learn to live with it, because that’s life in a box. Frida Kempff’s Knocking asks an unsettling question: what if the ordinary sounds of apartment living shouldn’t be ignored?

Molly (Cecilia Milocco) is on her own after a long stay at a psychiatric hospital. Other than some vague reference to an “incident,” we don’t know the nature of what brought her to the hospital, but she seems as though she’s forgotten how to interact with the world. Still in mourning over the end of a relationship (or perhaps the death of her partner, it’s never quite clear), Molly is painfully lonely, bereft of any friends or family to comfort and support her.

As part of her recovery, she moves into an apartment building where the hallways are lit a sickly green that’s all too reminiscent of where she just left. While Molly’s flashbacks of life with her girlfriend are sunkissed gold, her current life is stiflingly dreary, plunged into shadow, where even sunny days are muted. Her days are long, and her nights are interrupted by someone knocking on her ceiling. For most people this would just be a minor annoyance, but for Molly it quickly becomes a point of obsession. She believes it’s someone sending her a message, calling for help, a message that only becomes more urgent when she hears a woman weeping somewhere within the building.

Knocking asks an unsettling question: what if the ordinary sounds of apartment living shouldn’t be ignored?

Molly’s neighbors (all men, it should be pointed out) seem to be either annoyed or amused at her claims, and none of them are interested in helping her find out where the noise is coming from, though they’re more than happy to gang up against her and call the police when she demands answers. Are they simply ignoring what she hears? Are they working together to gaslight her? Is Molly, fragile as a bone teacup, simply imagining it?

Obviously I’m not going to spoil the ending of Knocking, except to say that it’s a bit anticlimactic. Based solely on visuals and Milocco’s intense performance, Knocking is as compelling a movie as you’re likely to see this year. However, they’re ill-served by its conclusion, which feels rushed, and as if screenwriter Emma Broström didn’t decide until the last minute how she wanted to end it. Up to that point, however, it’s a harrowing experience, and Milocco dominates the screen, playing a woman hanging on to her sanity by a gradually narrowing thread. Perhaps even more unsettling than her breakdowns are when she tries to create the illusion of being a normal person who buys fruit and plants for her new apartment, and ends up looking like an alien wearing human skin. That we don’t know what drove her over the edge in the first place makes it all the more disturbing.

Stories with gaslighting themes are all too timely right now, and Knocking serves the theme well, particularly in Molly’s interactions with her neighbors, some of whom act as if they know something she doesn’t. Most of the movie is relentlessly unnerving, which makes the pat ending so much of a letdown. It pulls no punches the rest of the time, why start then?