“When I tell people my story, they don’t believe it,” Bobby Shafran says at the start of “Three Identical Strangers,” a refrain that one may hear often in documentaries, but never seems like as much of an understatement as it does in Tim Wardle’s first feature. A rare nonfiction film that can devastate and entertain in equal measure, “Three Identical Strangers” tells of Shafran, Eddy Galland and David Kellman, three biological brothers reunited after living with separate families in their twenties, completely unaware of the others’ existence until Bobby attended the same community college Eddy did, a year after Eddy dropped out.

From the second Bobby recalls revving up “The Old Bitch,” a loving nickname for his beat-up car, to see if his classmates at Sullivan County Community are telling the truth about him being a dead ringer for Eddy, you know you’re going for a ride, with Bobby and Eddy soon joined by David, the best off of the three financially, who learned of his brothers’ existence by seeing their picture in the New York Daily News. The brothers not only look alike, but share the same gregarious spirit, making them a hit at New York clubs like Limelight and Copacabana after their story captured the public’s imagination in the 1980s. But while their bond was so immediate that they asked no questions of why they were split up in the first place, their adoptive parents had quite a few, which is where Wardle uncovers an even more surprising and unsettling story involving Louise Wise Services, the adoption agency that placed the orphans.

It would be a crime to say much more about “Three Identical Strangers,” but while it never loosens its grip on you, Wardle pivots impressively from a rollicking, pop-song laden yarn bursting with the same sense of discovery as the brothers had for each other to a sober investigation of murky ethical behavior and social conditioning, as the brothers each grew up under different circumstances of class and privilege before meeting each other at 19. Although one can occasionally feel the filmmakers conspicuously cutting off an interview just before something that might tip the hand for a later revelation, Wardle and editor Michael Harte structure the film brilliantly in dividing the brothers’ story into two distinct halves, channeling their exhilaration in the first section as they find fame and a sense of belonging with each other and their growing disillusionment in the back end as they come to discover how they were separated initially and begin to recognize what they may have overlooked in their initial excitement. (Not that these emotional currents are exclusive to one section – a sequence set to Billy Joel’s epic “Scenes from an Italian Restaurant” is about as expertly executed an emotional rollercoaster as you’ll see.)

With so many fascinating details surrounding their adoption and in the lives they led after, it would’ve been easy to get hung up at any one point in the brothers’ story, but “Three Identical Strangers” gallops along at a fervid pace, remarkably giving every twist and turn the necessary context and right tone to land one gut punch after another. An unbelievable story becomes all too believable in “Three Identical Strangers” and through the good times and the bad, you can’t look away.

“Three Identical Strangers” will play at the Sundance Film Festival on January 20th at 9 a.m. at the Temple Theater in Park City and the Salt Lake City Library at 6 p.m. in Salt Lake City, and in Park City on January 24th at 3:30 p.m. at the Redstone Cinema 1, January 25th at 3 p.m. at the Sundance Resort in Provo and on January 27th at the Prospector at 2:30 pm.