Based on the novel by Josh Malerman, Bird Box is the latest addition to both Netflix’s original film lineup and the horror subgenre featuring sensory deprivation. The post-apocalyptic thriller is allegedly the most-watched Netflix film to date, and with good reason too; it’s pretty dang effective.

The film starts after the apocalyptic plague has already set in. I mean “plague” in the Biblical vein of frogs and locusts and other pests, and not specifically in modern terms of a widespread disease. Malorie (Sandra Bullock) has two small children with her, and her only hope for their survival is to set off down the river toward a mystery signal that may be a trap, but is the only thing that gives her hope. Here’s where we realize that I, and Bird Box, are getting ahead of ourselves. Let’s go back to the beginning.

Malorie is an expectant mother who’s just trying to get through her pregnancy and on with her life. Her sister, Jessica (Sarah Paulson), is there to drive her to ultrasound appointments and keep her grounded in her impending maternal future. We hear news stories on the hospital waiting room televisions about various attacks and widespread deaths, but those are nowhere near them on the west coast. Nothing to worry about.

Well, if you’ve seen a single horror film (or family drama or romantic comedy, for that matter), there’s always plenty to worry about. Within what feels like the blink of an eye, the world that they know has torn itself apart, and Malorie is now in a big house filled with strangers just trying to survive. The threat outside is somehow simultaneously creatures (From where? Who knows?) and is transmitted like an ocular virus. If you see what should not be seen, you will die.

I truly respect horror films like Bird Box that don’t over-explain the source of the horror. Horror exists in brevity and the unknown. There’s also an enormous difference between a film that clearly has no idea what the constraints of its monster are, and one that has full awareness, but doesn’t tell the audience all it knows. Bird Box feels like the latter, and only lets us glimpse (metaphorically) at what’s terrorizing our few survivors.

Watching the sometimes ineffective trials of trying to stay alive is where Bird Box shows off its horror chops. The movie shows early that it’s not afraid to kill off major characters or well known actors, which serves to chip away at our collectively suspended disbelief.

Unfortunately, the movie’s story structure consistently undercuts the tension and terror it had done an exemplary job of crafting. The film spends most of its running time toggling between the past and the present; from one tense scene to another. This means that we see a constant parade of conflict and swift resolution, and not any overall or sweeping crescendos of horror. This technique can, and has, worked for other films, but here it just feels jerky. Add to that an ending that veers a bit too far into saccharine, and thus feels out of place in this brutal world, and Bird Box starts to show its seams of imperfection.

Overall, Bird Box is a solid new entry into sensory deprivation horror, and perhaps a greater sign that Netflix just might know what it’s doing.