“Why are you doing this to us?” a tied-up Liv Tyler asks a trio of masked murderers at the end of Bryan Bertino’s The Strangers.

“Because you were home,” one replies.

Before we learn any further information about the killers, the movie ends. That’s it; no big twist or reveal; no backstory, no explanation. It’s like those unsolved murder mysteries you hear about where the pieces don’t fit into a tidy story, where unknown attackers kill for no discernible reason. And those are always the stories that leave you with an unshakable chill.

Back on May 30, 2008 when The Strangers first hit theaters, many critics took issue with the savage, inexplicable motives of its title characters. One critic wrote it off as a “sadistic home-invasion flick”; another denounced the film as the “cheapest, ugliest kind of sadistic titillation,” while Roger Ebert vented about the “maddening, nihilistic, infuriating ending.” Sure, Bertino’s film is full of nerve-jangling brutality – more often of the psychological variety than of the purely violent – and the villains are not fleshed-out characters. But all of that is what makes The Strangers a great horror movie 10 years after its debut.

The Strangers freaked me so much the first couple times I saw it that when I decided to rewatch it for its 10th anniversary last week, I had to do so in the middle of the afternoon. Ever the masochist, I was once brave (insane?) enough to watch it in a remote Oregon cottage in the middle of the night. I survived that experience, but knowing I would be alone in my apartment the night of my latest viewing, I decided to do it in broad daylight. Too bad such precautions hardly made a difference, since it still scared the crap out of me.

Rogue Pictures

Bertino’s film opens in the middle of a calamitous evening for Kristen McKay (Tyler) and her boyfriend James Hoyt (Scott Speedman). She’s just rejected his marriage proposal and now the two have to bear the awkwardness of returning to his father’s cabin, showered with rose petals and romantic candlelight. That heartbreak is nothing compared to the nightmare these two are about to have though. Just as they’re easing into break-up sex, there’s a sudden knock at the door. James answers to find a strange woman standing in the shadows, asking for a man neither of them don’t know. But as she turns away, the woman cooly adds, “See you later.” Not long after James leaves for the store, Kristen is bombarded by another series of booming thuds at the door, these ones louder, angrier, and more menacing.

It’s simple, realistic scares like the sound of a late-night knock at the door that make The Strangers feel like a horror movie that could happen to you. Watching it has always reminded me of an eerie childhood memory when a strange man knocked on my family’s door late at night, hovering in front of the peephole for a few moments, then walking away. It happened to Bertino too, and is what gave him the idea for the film. He later took that same idea to a mobile home park for this year’s sequel, The Strangers: Prey at Night.

In rewatching the film this time, I was surprised to realize how little onscreen violence there is – besides a grisly shotgun to Glenn Howerton’s face, the bulk of the film’s bloodshed is reserved for the grisly murder in the final minutes. Instead of relying on gore, Bertino creates panic and terror out of moments of inactivity. The most frightening parts are uncomfortably still, where violence is only threatened, not enacted (yet). It’s when James and Kristen watch the Dollface killer staring back at them from the driveway; they’re inside and she’s outside, far away and seemingly unthreatening, yet it’s a moment flooded with unease.

Bertino turns another quiet scene into the movie’s scariest moment: When we see the burlap sack killer inside the house – a moment that jerked me out of my chair during my recent rewatch (which, again, was in broad daylight). It’s an effective jump scare because Bertino and his cinematographer Peter Sova shoot it without horror gimmicks. In a static wide shot we watch Tyler’s Kristen walk into the kitchen, then just behind her, out of focus, the man’s white mask slowly appears from the shadows. Most filmmakers would heighten the moment with a blare of the score – the only sounds in this scene are the low hums of the vacant nature around them – or cut to a close-up of the killer to emphasize his presence. Instead, the man just lingers far off on the edge of the frame, then quickly vanishes before Kristen notices.

The Strangers messes with your head. Like its trio of killers, it does the opposite of what you expect. Instead of revealing a familiar character as the film’s villain, the Strangers remain faceless and nameless. Instead of attempting to murder the couple right away, they take their time playing mind games. Instead of relying on modern innovations for scares – horror about technology was all the rage in the early 2000s after The Ring – The Strangers has the classical quality of a spooky campfire tale. After Bertino puts you through 90 minutes of terror, the film ends on something unexpected and even more unnerving than a knife to the gut: that four word response, “Because you were home.” It’s all just an unfortunate case of being in the wrong place at the wrong time.

Most horror scenarios ascribe some sense of rationale to the evils that ensue. A vengeful spirit haunts because that’s whats ghosts do; a killer murders for revenge; a child is possessed by demons because that’s how the Devil works. But the scariest things are often those that lack reason. The completely random nature of The Strangers is what turned a simple home invasion story into a timelessly spooky one. It’s a movie that suggests the horrifying things we see on film could happen to us in the real world, anywhere, at anytime, by anyone, and we’ll never know why. What’s more frightening than that?