In June 1994, Nicholas Barclay, a blond, blue-eyed 13-year-old from San Antonio, Texas, disappeared on his walk home from a basketball game with friends. Over the next three years, his family agonized over his fate. “You know you’re not going to find him alive, but you just want to find out what happened to him,” his older sister Carey, 31, says early in The Imposter.

Then, in 1997, comes an amazing break in the case, almost too amazing to be believed. Police in Linares, Spain, discover a boy huddled inside a phone booth, with no identification, reticent to talk and tell them how he got there. Eventually, he was sent to a shelter where he finally broke his silence, telling authorities his name is Nicholas Barclay, he was kidnapped three years ago by a child-trafficking ring and smuggled overseas. He had recently escaped his captors and was terrified. He just wanted to go home.

The title of Bart Layton’s quasi-documentary The Imposter, which mixes talking-head interviews with dramatic re-enactments of certain events, lets you know from the start the man is lying. But you’d doubt his story no matter what the film was called. Frédéric Bourdin, his real name, looked too old to be a teenager (he was 23 at the time), and his brown eyes and hair were nothing like Nicholas’. He also sported a thick French accent. Still, he was convincing enough to have the U.S. State Department fly his sister Carey to Spain to get him. At the airport, when they meet, you expect her to recoil and immediately expose him as a liar. Instead, she tearfully embraces him as her brother and brings him back home to Texas.

And then things get really weird. The story of Bourdin, a Tom Ripley-esque con artist who specialized in impersonating missing people and creating false identities for himself, made international news in 1998 when his sham in Texas was exposed and was sentenced to six years in prison. The fascinating aspect of The Imposter, though, is why the missing boy’s family believed his story. Nicholas’ mother, a woman with multiple health problems who worked the night shift at a convenience mart, accepted him blindly. His uncle Bryan, a seemingly shrewd and level-headed man, also bought the story.

Bourdin, who is interviewed in the film exuding an unmistakable air of pride and self-satisfaction, says he had an answer for everything. How had the color of his eyes and hair changed? His captors had poured acid on him. How about the French accent? From all the time he had spent overseas. Why did he need to have friends and relatives pointed out to him in old photos? The horrible ordeal he had endured had erased part of his memory. Even an FBI agent who poked at every detail in his story couldn’t find a flaw.

Most puzzling of all, though, is how the family didn’t immediately sense this man was not their missing son. The Imposter subtly argues that the Barclays, offered a way out of their perpetual grief, no matter how implausible, seized on it without dwelling too much on the details. Why would Bourdin pretend to be Nicholas, anyway? Certainly not for money (the family was lower middle-class) or prestige (San Antonio was much duller than his previous stomping grounds of Europe). Was he on the run from a crime, wanted by authorities? Had he come to Texas to find new prey?

Bourdin might have gotten away with the whole thing if not for Charlie Parker, a private investigator who became obsessed with the case and noticed that Bourdin’s ears looked nothing like Nicholas’ (ears are as unique as fingerprints). Parker’s inquiries lead The Imposter in a darker direction filled with sinister implications (and one possible solution to the case). But the detective was ultimately unable to find the boy, who remains missing.

Parker did, however, manage to put Bourdin away, who is seen near the end of the film dancing madly in what appear to be prison fatigues, deliriously happy for the attention and apparently unfazed by incarceration. Since his release from prison, Bourdin continued assuming false identities in various countries around the world, earning him the name “The Chameleon,” until he finally married in 2007 and retired from the impersonation game. The great, inconsolable pain of Nicholas Barclay’s family, however, continues.