On the surface, the central mystery driving Ursula Macfarlane’s documentary The Lost Sons is a straightforward one. It’s a film about a man’s hunt for his true identity. It quickly becomes apparent that the search will instead be a twisted and unbelievable journey of discovery, with a sequence of events that would seem far-fetched in any fictional film.

Debuting at this year’s SXSW, The Lost Sons tells the story of Paul Fronczak—a man who recounts his life story straight to camera. At age 10, Fronczak discovered he had been stolen from his mother’s arms while she was still in hospital shortly after his birth. His mother Dora had willingly handed him over to a woman dressed as a nurse, who’d advised the new mom that her infant was scheduled for an examination by the doctor. It was hours later when hospital staff realized the woman had fled the building and baby Paul was gone.

A lengthy search for the missing baby followed for two years later until, lo and behold, a young boy approximately Paul’s age was abandoned in New Jersey. Cue a tearful and grateful reunion.

But just as The Lost Sons starts chugging to a somewhat sluggish but happy conclusion, new twists arise and deepen the Fronczak mystery.

I’d be remiss to give too much of the film’s revelations away, but the events that transpire really would be dismissed as too “far-fetched” in any fictional narrative.

It should come as no surprise that CNN Films is behind The Lost Sons. The doc fits squarely in with their previous releases, Three Identical Strangers and The Imposter, both of which are documentaries that peeled mysterious layer after mysterious layer back like an onion. Utilizing interviews with key players, archival footage, and re-enactments, Macfarlane crafts a story here that is both entertaining and interesting.

The Lost Sons is a personal and specific story and its subject a fascinating one. Though at one point he disagrees with a guess that viewers will “f***ing hate” him, it’s true that the handsome Fronczak is extremely likeable. He is charismatic as he tells not just the story of his early years, but of his time as an actor and a member of a rock band. He is a man driven to the point of obsession, convinced he can never know who he is without all the clues to his past, no matter what consequences that may have in his present life.

Genealogy fans will appreciate the second half of the film, as it features a group of all-female DNA researchers digging deeper into Fronczak’s past. While most of the film is structured in the standard way, with subjects addressing the camera head-on, there is one moment in the film’s last act where, along with Fronczak, the viewer feels like an active participant in a sad and deeply troubling story told by his former babysitter. Macfarlane rightly lets some of the discoveries play out at a leisurely pace but knows when to ramp up the tension with quick cuts as the story rockets to climax, delivering a thrilling narrative in which it appears the truth is always stranger than fiction.

The Lost Sons currently does not have a release date outside of SXSW, which runs March 16-20.