The Gullspång Miracle begins as a story of a family reunited and then twists into something much stranger. When the two sister May and Kari go to close on an apartment in Gullspång, Sweden, they encounter the seller, Olaug, who bears a shocking resemblance to their elder sister, Lita. But Lita died thirty years before, of an apparent suicide. As the three begin to investigate the strange similarity between Olaug (who also goes by Lita) and Lita, further questions are raised, about family, about religion, and about the reality of what happened to Lita all those years before.

The Gullspång Miracle proceeds along with the energy of a family mystery and elements of a ghost story, showing the tangential connections between Olaug and her (possible) family, and the past that haunts them all, via direct interviews and interactions as well as archival family footage of Lita. To say too much about the overall story would be to spoil the twists and turns of the mystery, which is part of the fascination of the film. In many ways, The Gullspång Miracle parallels earlier documentary mysteries like Three Identical Strangers, released several years ago. If you think you know what’s coming, you probably don’t, and the film is sure to keep you guessing.

It seems odd to treat other people’s lives as a mystery to be solved, but The Gullspång Miracle allows a certain degree of indulgence in the strange permutations of family history while at the same time respecting its subjects and evading, for the most part, judgment upon them. What actually happened to Lita, who Olaug is (or isn’t), the motives and desires of the newfound family, combine together in an increasingly strange narrative as compelling as it is eerie. At its base is also a question of what family actually is—whether it is blood relation, upbringing, nature, or some strange combination of personality and prejudice. All come into play as the film proceeds. Loyalties and desires shift, people change, and the deeper the family delve into their past, the more they question how much they really want to know.

The Gullspång Miracle also works to develop its own artifice. It opens with the depiction of the two sisters seeing the apartment for the first time but highlights how the director Maria Fredriksson instructs them as they re-enact the scene. Maria reappears throughout the film as she interrogates the family’s shifting allegiances and emotions in the increasingly eerie tale of Lita and Olaug, including interjecting her own emotions about the story that was brought to her, and the story that the film it has become.

Many documentaries at Tribeca this year have a haunted quality, as though they’re being shaped by ghosts of the forgotten. The Gullspång Miracle’s otherworldly elements hang at the peripheries, as the various subjects give nothing away at first, then burst out with declarations of love and hate, or even fantasies of violence. It is a haunted documentary, seething with animosity and mysteries just beneath the surface, like the still calm on the lake where Lita may or may not have committed suicide. The deeper The Gullspång Miracle goes, the more disturbing it becomes.