Craig Zobel’s “Compliance” may be the creepiest movie of the year. It has no physical violence, no sex, barely even a raised voice – and yet it burrows into your brain and keeps burrowing, the longer you watch.

Based on a set of actual incidents, “Compliance” starts out simply enough: Sandra (Ann Dowd), the manager of a fast-food restaurant, gets a phone call from the police – and the officer on the phone says there’s a problem.

One of Sandra’s employees, a young woman named Becky (Dreama Walker), has allegedly stolen the wallet out of a customer’s purse while waiting on her. The police need the manager to hold Becky until the police can arrive.

As Sandra sequesters Becky in the back room and questions her about the charges – which Becky strenuously denies – the cop continues to talk into Sandra’s ear: Of course Becky’s going to deny it, he says. So he needs Sandra to search Becky for him. And not just search her – but strip-search her.

Quietly, without a lot of shouting or conflict, Sandra insists on doing what she’s told – and Becky, claiming innocence, complies, for fear of losing her job. Naked, finally, she seems to be innocent because Sandra comes up empty-handed.

But when Sandra has to get back to running the restaurant, the cop insists that she leave someone to watch Becky until he can get there. So Sandra hands off the phone to one of her other (male) employees. Once the cop gets him on the phone, the process begins again: The cop tells the new employee that he just needs him to search Becky – to strip-search her. Having not been in on the initial search, the employee complies.

And so it goes. Ultimately, of course, it turns out to be a hoax: Someone sitting at home has been manipulating all of these people with nothing more compelling than his voice and his ability to convince them that they’re doing their duty.

Though it seems fishy enough when you watch it in a movie, this actually happened dozens of times. And each time, the restaurant managers complied with the “cop” on the phone, putting a younger, more vulnerable employee through a humiliating exercise – sometimes more than once, over the course of several hours.

Zobel’s film, which only runs 90 minutes, can feel excruciating, as the seemingly bright but ultimately helpless Becky endures repeated invasions of her privacy, as well as her person. Sandra seems almost as much of a victim: She should be in control, yet she finds herself doing things she normally wouldn’t do, justifying them with the belief that she’s helping the police.

The actions depicted are almost as unsettling as the questions that “Compliance” raises. Ultimately it comes back to the Adolf Eichmann defense: “I was only following orders,” as though that excuses the most horrendous behavior or, in this case, stripping a young woman of her dignity.

Dowd brings gravity – though blinkered gravity, at that – to the harried, unsettled manager. Walker is surprisingly unflappable as the put-upon young woman, seemingly willing to do whatever she’s asked to prove her innocence. Yet she shows the toll this assault on her begins to take.

“Compliance” is an upsetting film, hard to watch because it so quietly and casually goes about its business of pushing your buttons. It’s hard to say you’ll enjoy it – but if you’re looking for a film that shoves you way out of your comfort zone, this one will do the trick.