A friend who also likes horror movies asked me, “Was this movie one that made you jump, or one that was just creepy?”

I answered, “Yes.”

Oculus is a good old-fashioned horror film that relies less on gory torture and more on atmosphere and building a sense of dread.

Told in present time and flashbacks, it chronicles two siblings who, when younger, suffered through the unspeakable trauma of their father murdering their mother—after their dog disappears, a mysterious woman skulks around their house, and their mother goes crazy, no less. Not a Norman Rockwell childhood by any means. More of a Stephen King/Clive Barker situation.

Just when you think you know what’s going on… the audience is jerked back into reality

The son, Tim (Brenton Thwaites), manages to stop his father by shooting him. He is sentenced to years in a mental institution, and the film opens to him being released. His doctor says he has come to terms with the ordeal he suffered through. His doctor says he is sane and fine to re-enter society; that everything is rational and based in reality.

His sister Kaylie (played by Karen Gillan), says he is fine too, but everything they experienced was perpetrated by an antique mirror possessed by evil.

Kaylie has spent her time learning the history of the mirror she believes is the root of their parent’s demises, and guilts her brother into honoring a promise he made before the police carted him away when he was ten. She tells him he promised to help her destroy the mirror and end the evil. Her obsession with the mirror and its purported malevolence drives her to create a Rube Goldberg-esque system to ensure they’ll be safe while they prove her point.

The nice, subtle touch in this film was the effort the filmmakers made to dust everything with ambiguity. Kaylie insists Tim was brainwashed when he tells her he remembers things differently (the dog didn’t disappear in the presence of the mirror; the dog was sick and euthanized at the vet’s!). Tim tells Kaylie that all the information she’s found that she says is true is just coincidence and she never had the help she needed to understand what happened in their childhood. The movie twists back and forth: is Kaylie right? Is the mirror host to an evil spirit that drives people insane and murderous? Or is Tim the one in his right mind, and she is creating ghosts to cope?

There is an answer in the end. Kind of. Oculus heads down one path, showing us what both siblings are experiencing in horrifying, unsettling detail. The malevolent force manifests itself visually and is downright creepy. It’s manipulative. It’s insidious. And just when you think you know what’s going on, at the very end the audience is jerked back into reality—forced into an outsider’s viewpoint where things look very, very different.

The manipulation wasn’t just for the characters in the film; it was for the viewers as well. Although it seemed straight-forward at the time, the last few scenes leave a disconcerting sense of maybe what you thought is wrong. That maybe this seemingly innocuous independent horror film actually touched on some deep-rooted, primal fear of going insane, being insane, while no one around you understands. The fear of being alone in your reality, with no hope ever getting back to ‘the real world.’

Those are scary thoughts indeed, and made this movie an effective little gem.

Oculus, directed by Mike Flanagan, written by Mike Flanagan and Jeff Howard; starring Karen Gillan, Brenton Thwaites. It is available through Netflix, Hulu, Amazon.