The very first thing you see in Craig Zobel's Compliance is a huge title card reading "INSPIRED BY TRUE EVENTS." This turns out to be necessary information, because this story—of an 18-year-old fast-food worker who is detained, strip-searched, and sexually assaulted by her co-workers—almost completely strains credibility. Watching Compliance, one wants to assume that writer-director Zobel has invented certain elements for dramatic purposes, if only because one is hesitant to believe that real human beings could be naive, gullible, or craven enough to make the decisions the characters in this movie make.

As it turns out—though names and a few details have been changed—all the major elements of this story are taken, directly and faithfully, from an actual incident that occurred in a Kentucky McDonald's in 2004. Not only did more or less everything happen as it happens here, but—as we are informed at the movie's end—dozens of other frighteningly similar incidents occurred around the country.

But how much should that matter? The film, after all, is presented as a work of art, not a documentary: it is not enough to know the events took place in real life; what we see on the screen must be convincing as well, and it is here that this movie falls slightly short. Emotionally harrowing, thought-provoking, and never less than fascinating, Compliance nevertheless fails to make us completely believe in all the turns of this lurid tale, and never manages to offer much insight or illumination into how and why events happen.

Compliance takes place in a midwestern-branch of the fictional fast-food chain ChickWich, on a busy Friday night when tensions are already running high. Manager Sandra (veteran character actress Ann Dowd, excellent here) already has her hands full: the restaurant is understaffed, someone left the freezer open and spoiled a bunch of stock, and a spy from headquarters may be dropping by to check up on things. (Zobel and his cast succeed in making the world of the ChickWich a convincingly real environment, and hint at the minor grievances, workplace politics, and subtle resentments that could help explain, a little, some of the dehumanizing social experiment that ensues.)

And then Sandra receives a phone call from a man (Pat Healy) who identifies himself as an Officer Daniels, and says that pretty counter-worker Becky (Dreama Walker) has been observed taking money from a customer's purse. Officer Daniels is unable to get down to the restaurant right now—he's busy with the "larger ongoing investigation"—so he needs Sandra to detain Becky and help him recover the money.

That Sandra accepts this information at face-value—and fails to ask any of a dozen logical follow-up questions—is only the first of many, many moments at which one wants to scream at the characters on the screen to stop and think for a moment. Does it seem right that a policeman would conduct this entire investigation over the phone? Does it make sense that a customer was stolen from, and yet left the property without saying a word? Would it really, under any circumstances, be legal or acceptable for private citizens to search their co-worker as part of a criminal investigation? Would it not be more logical to wait for an actual policeman to arrive in person?

But Sandra never asks these questions: "Officer Daniels" enlists her help through slapdash psychological manipulations—alternating threats and flattery—and every one else who is drawn into the situation accepts that they are talking to a cop because Sandra tells them so. And so begins an ordeal for Becky that lasts several hours, beginning with a search of her possessions, escalating to a search of her person, and continuing—on the increasingly bizarre orders of "Officer Daniels"—through a series of progressively horrendous violations.

This story itself is horrifying enough, and fascinating enough, to ensure that Compliance will be one of the most talked-about movies of the year. (It was the most controversial movie at Sundance—where the conversation turned ugly during the post-screening Q&A—and it has reportedly resulted in walk-outs in many theaters.) And the themes it explores—of the banality of evil, of blind obedience to authority, and of good people who do nothing to stop an injustice—are always timely and important; the movie often feels like a recreation of a troubling psychological experiment, like Stanley Milgram's controversial "shock-treatment" study at Yale, or the Stanford prison experiments. See it with a friend, and you are practically guaranteed a lively and interesting conversation after the show.

But, while both Zobel and his cast handle this provocative, stranger-than-fiction material fairly responsibly, Compliance feels like it relies too strongly on its sensationalistic premise and brings too little else to the table. Surveillance footage from the real incident shows what happened, but it is without audio: Zobel has been forced to imagine how it happened—what words were spoken by both the caller and the victims of the hoax—and his screenplay does not fully succeed in carrying us believably down the rapid descent into abomination these characters take. In the final act, Sandra's fiance Van (Bill Camp) is enlisted to watch over Becky, and the story takes its most sadistic and least believable turns. Camp is excellent in the role—slightly dulled by alcohol, and perhaps more than a little uncomfortably titillated by the power he is abruptly handled—but nothing in Zobel's dialogue really explains why he would do what he does, or—more importantly—why Becky would go along with it.

And here we come to the largest problem in the film: Becky is simply not convincing. Dreama Walker gives a brave, admirable performance, but—through no fault of her own—she is terribly miscast in an underwritten role. Walker is 26 years old, and a stunning Hollywood beauty: she makes a respectable stab at playing an 18-year-old fast food worker from rural Ohio, but she simply has too much worldly strength and self-possession for us to believe that she would so easily accept the treatment she receives. Zobel's screenplay does her no favors either, because in the early scenes he chooses to emphasize Sandra's resentment of Becky by making the younger woman sexually confident—we hear about the three different boys who are chasing her—and a bit of a smart-ass. She seems like the kind of girl who would tell her accusers to go fuck themselves, and the fact that this never happens seems puzzling.

In making these choices, Zobel seriously undermines the believability of this hoax's victim—her reactions come across as unreadably enigmatic—and by focusing the thin motivation on personal and sexual issues he misses some real opportunities to say some genuinely illuminating things about class, education, and blind obedience. The real victim in this case was an 18-year-old young woman named Louise Ogborn, who desperately needed to keep her minimum-wage job in order to assist her unemployed mother with medical bills: interviewed by ABC Primetime in 2005, Ogborn comes across as heartbreakingly naive, even in the aftermath of everything that has happened to her. She trusted the police, without question; she trusted her manager to do what was best. "My parents taught me, when an adult tells you to do something, that's what you do, and you don't argue," she says in the interview. "If somebody smacks you on the hand, you listen." That kind of innocence—and the extreme vulnerability to authority that it creates—is sadly missing from the character in Compliance.

(The full ABC news story is here, but be aware that watching it will amount to full spoilers for Compliance, and that the video itself—which contains the actual surveillance footage—is extremely disturbing.)

Compliance does a great many things right—a few poor aesthetic choices aside, Zobel and his fine cast deftly avoid a lot of ways in which this material could have turned unforgivably lecherous and exploitative—but the film ultimately feels like a well-crafted recreation of what happened, rather than a smartly insightful exploration of why it happened. We feel sympathy for Becky, but we do not really understand her behavior; we feel superior to Sandra and the other perpetrators, but we are never convincingly persuaded that we ourselves might, under certain circumstances, be capable of such actions. Compliance is a good movie—one that will provoke a great many worthy conversations—but Zobel's inability to delve deeper into the hows and whys of this story prevents the film from achieving greatness.