From the very beginning ofThe Imposter, we know that the young man who in 1997 claimed to be a teen who disappeared from San Antonio three years earlier is a fraud. He is a Frenchman, who had been living in Spain. He is 23. He just wanted to be anybody but himself.

Yet director Bart Layton, who until now has helmed only a handful of TV documentaries, keeps you more than merely in suspense throughout the film’s 99 minutes—he keeps you unsettled, haunted, enthralled. This is the story of Nicholas Barclay, the Texas boy who was 13 when he vanished. But it’s more about Frédéric Bourdin, the man who stole Nicholas’ identity, a crime of both wiles and opportunity. He provides commentary throughout the doc, taking us step-by-step as he fooled first the authorities and then Nicholas’ family themselves.

Nicholas’ disappearance didn’t make a splash when it happened (“it wasn’t news to [the papers],” his mother, Beverly, says), but his supposed re-emergence eventually did, all because of the stranger the boy’s relatives suddenly found in their midst. Frédéric’s crime, while planned, quickly became a dance of improvisation. Sure, with a hood and low hat, he could pass himself as the kid in the FBI’s black-and-white photo faxed over to the Spanish youth home from which Frédéric imitated a social worker, claiming he had an unidentified kid who said he was from the States. Phone calls were made, and soon Nicholas’ much older sister, Carey, was on a plane. “I washed her brain,” Frédéric says matter-of-factly.

It was only then that he glimpsed a color photograph of Nicholas—all blond hair and blue eyes, whereas Frédéric’s were brown/brown. His hair was easy enough to change, but his eyes? His reaction: “Fuck, you know? Fuck fuck fuck fuck fuck.” Frédéric was sure he was toast.

But Frédéric continued to pass the Nicholas test, and how it all went down—along with a potential why that will turn your stomach once you realize its possibility—is what makes The Imposter so fascinating. Reenactments can be cheesy, but Layton incorporates these shadowy re-creations of real-life events seamlessly and spookily, sometimes with Frédéric dubbing the scenes. In some cases, he intercuts these he’s-gonna-get-caught moments with shots of Frédéric smirking.

More unnerving are Layton’s sympathy for Frédéric and portrayal of Nicholas’ relatives as dumb rednecks. The con man? He had an ugly childhood, unwanted both before and after he was born, and was just looking for love. He insinuated himself into a grieving family, and did so smartly. That family, though? Well, Layton could have edited out comments such as Carey’s “Spain: Isn’t that, like, across the country?” and Beverly’s “My main goal in life was not to think,” which she says when asked how she could have believed Frédéric was her son.

As a result, the tragedy of a boy’s disappearance becomes lost. It’s difficult to feel bad for Nicholas when you’re so caught up in the stranger-than-fiction subplot of how one man managed to become him. Even though his own mother was willing to tune out, you may feel a little guilty when you do, too.