One of several Blumhouse films released in concert with Amazon, Black Box is a gripping bit of high-concept sci-fi/horror, ambitious in its themes but deliberately tight in its structure. More than anything, it shows the value of director Emmanuel Osei-Kuffour’s conviction and control: by committing to his story and following it closely, he makes the film’s shifting genres and stakes and cast work, and none of the changes or revelations feel cheap. This could be a whole season of prestige TV, but it’s better for being a mere hundred minutes; the fact that there’s no easy stopping point but the end aids the sense of unity and relentlessness. It’s like being strapped into a carnival ride and propelled into the dark. Something’s happening in here, and all you can do is wait, heart pounding, to come out on the other side.

Nolan (Mamoudou Athie) survived a car crash that killed his wife and left him with a traumatic brain injury that’s severely impaired both his short- and long-term memory. He’s trying to take care of his ridiculously adorable young daughter, Ava (Amanda Christine), but he’s painfully aware that she’s really the one taking care of him: she reminds him of his schedule, shows him a picture of his old boss and quizzes him on her name, and cooks their dinners. Her school is getting concerned about the number of pickups Nolan has missed. And Nolan has to make the connection between his bruised, bloodied hand and a dented wall in his house: apparently he punched it out of frustration, though his loyal friend Gary (Tosin Morohunfola) says that isn’t like him at all. He was once a top-notch photographer, but now his skills have gone lackluster; the person who used to take those pictures just doesn’t exist anymore, not in the same way. Nolan needs, desperately–for both his sake and Ava’s–to recover his memories and sense of stability. And so, after much hesitation, he finally returns one of the many phone calls from the persistent Dr. Lilian Brooks (Phylicia Rashad), who claims that her “black box” device can help bring him back to himself.

But the black box brings up memories that seem at odds with the stories Nolan has been told about himself. Was his marriage really as happy as his friend has told him it was? Who is he, really? And what the hell is the backwards crab-walking man (Troy James) with breaking bone sound effects doing following him through his dreams and trying to choke him to death? Is it his subconscious trying to protect him from realizing something he doesn’t really want to know?

Osei-Kuffour’s artful trick here is in following this story closely, making it emotionally compelling, and then upending it without losing any of its forward momentum. He turns an inward story outwards, making it less psychological and more philosophical, less horror and more science fiction drama; the questions raised by the film in its second half are different from those in its first, but they’re just as interesting to consider. The acting–especially from Athie–is strong, the script is clever, and some of the visuals are striking. Troy James’s Backwards Man (and his accompanying Foley work) has the potential to become a horror icon. But it’s the muddle of loss and uncertainty and meaning, the sheer multiplicity of piled-on concerns, that really gives the movie its lingering impact. Osei-Kuffour is definitely a filmmaker to watch out for.