The documentary Three Identical Strangers starts off as a happy reunion of three young men who find out they’re long-lost brothers. But it doesn’t take long for the viewer to realize the whole thing is not going to end well. When the brothers find out they were separated at birth for a secret research experiment, their joy turns to devastation. And as I watched, so did mine.

Available via streaming services including Comcast’s On Demand, the movie chronicles the lives of Eddy Galland, Robert Shafran and David Kellman. When 19-year-old Robert arrives at a small community college in 1980 and is greeted by strangers as a an old friend, he is mystified. He soon meets a classmate who introduces him to Eddy, who shares his looks, birthday and adoption story. The brothers become a media sensation, profiled in newspapers and on talk shows nationwide. The publicity leads David to realize he’s actually the third of the separated siblings.  The boys go viral before going viral was even a thing, embracing  their fame with a bachelor pad and club hopping, an appearance in a Madonna movie, and even a Manhattan restaurant named Triplets. Everyone marvels about their shared interests and mannerisms, even though they were raised in very different families. It’s a very 1980s phenomenon, and I couldn’t help but get swept up in the fun they were having.

The first sign I had that something was not right was when I realized that the documentary, filmed some 30 years after the reunion, only has interviews with two of the brothers. Where was the third?

In the film, joy soon leads to confusion and anger. The families confront the New York City adoption agency that placed the boys, demanding to know why they were never told the siblings existed. The adoption agency claimed it would have been too hard to place all three children in one home. But soon an author writing a book about twins learns there was a much darker reason. The boys, and other sets of twins from this same adoption agency, were separated so researchers could study how different parenting styles would impact children who were genetically similar. You may have heard of the debate over nature versus nurture: is it our DNA or our surroundings that has a greater influence? The study, led by the late psychologist Peter Neubauer, followed the boys into their teens with questionnaires and observation. Its existence was a closely guarded secret – the parents were told it was a study about adoption – and its results were never published.

Discovery of the study devastated the brothers. They felt robbed of their childhood and manipulated as lab rats. While they dealt with this revelation, they also struggled with the realization that the similarities so obvious upon their first meeting masked some very significant differences. As the brothers grew older, started families,  and went into business together, they saw that their upbringings had instilled different work ethics, values and beliefs. Disagreements developed, and they were no longer the carefree trio. They also saw signs of mental illness, which they later suspected might be another reason their family was targeted for the study.

The movie entertained, but also made me think —  not a bad combination for a lazy Friday after Thanksgiving. It inspired some serious discussion about nature versus nurture, the ethics of research and the effects of overnight celebrity. We never get answers about whether the study learned anything worthwhile. To me, it was just a glaring example of the scientists’ arrogance at playing God. I felt terrible for the two adult brothers still living today. When we finally learned what happened to the third, it was heartbreaking. Growing up with four siblings, there have, of course, been times when I wished they didn’t exist. But I also can’t imagine never knowing them. While the brothers reunited at 19, the years they spent apart – and the knowledge of why they were split up – haunted their entire lives.