Sleep Tight has its virtues–for one thing, it has an exquisite and almost unbearable sense of dread–but it mistakes darkness for substance. Horror doesn’t need traditional logic–and thank God, because so much of horror never bothers with it–but it does need a sense of fair play, and Sleep Tight doesn’t have that.

The movie focuses on Cesar (Luis Tosar), a dour apartment concierge who mopes about in a nihilistic, depressive funk, unable to find any real happiness in life. He opts for the well-known therapeutic treatment of ruining other people’s lives, particularly zeroing in on the sunny Clara (Marta Etura). He stalks Clara in an effort to make her miserable … only stalking isn’t exactly the right word to describe his intense, frequent home invasions. Sometimes he prowls around, engaging in juvenile jackassery like tampering with her beauty products to give her a rash. Sometimes he gets inventive, planting mail-ordered cockroach eggs everywhere in her apartment. And almost every night, he waits until she falls asleep, chloroforms her into unconsciousness, rapes her, and then cuddles her until dawn.

This is all, of course, horrifying, though it’s weighed down slightly by the fact that the movie keeps such a tight focus on Cesar, rolling around in his morose psychopathy without really putting in much time with Clara. But for a time, there’s some good tension to be found, because the movie gestures towards the realistic acknowledgment that this level of evil is, you know, kind of a time commitment. Cesar keeps being late for his shifts, putting his job in jeopardy. He’s spending so much time on Clara that he’s essentially risking his access to her, which is a semi-interesting conflict. And his more chaotic, randomized attacks against other people’s happiness have the potential to backfire, especially since Cesar’s choices are often shortsighted at best. He’s managed to frame a lower-rung employee for the stalking, but the second the behavior continues now that that kid’s gone, he’ll be toast. On top of all of that, the little girl across the hall from Clara has seen him creeping in and out, and she’s requiring regular bribes for her silence. When he’s buying a kid’s cooperation with money and, in one case, a porn DVD, you’re waiting for this to all backfire spectacularly.

For a second, it does. Cesar loses his job. It seems like this should drive him to one final, overt act that will bring his house of cards crumbling down.

But then, for no apparent reason, the film starts to cheat wildly, stacking the deck in his favor. He’s fired–but inexplicably still allowed a few days of access to the master-keys. Clara’s boyfriend finds him skulking around her apartment, but they eventually (temporarily) buy his clumsy excuse. Clara–now pregnant with what we know is Cesar’s child–spends several nights away and realizes she’s getting much better sleep, as are the miracles of not being chloroformed every night, but she fails to put the pieces together. Cesar gets the upper hand in a fight. None of his other bad bits of job performance come back to haunt him. And he suddenly turns suavely dangerous enough to terrify the little girl into lying to protect him, even though she has, up until now, been smart and hard-nosed to his sweaty, fumbling nervousness.

Sleep Tight wants you to be horrified by the unpunished and sickeningly thorough destruction of Clara’s life, complete with one final dark flourish, but it loses its narrative integrity getting there. The reckless, spiraling-around-the-drain dipshit we followed for the first half of the movie doesn’t inherently have the chops to get away with what he’s done, so the story has to help him out. It has to give him a boost and give all the other characters a boot on the neck to hold them down. And it doesn’t leave you thinking about tragedy and evil; it just leaves you thinking about weaknesses in the screenplay. It’s one of the few cases I can think of where the ending is haunting … but also deeply annoying.

Sleep Tight is streaming on Shudder.