Twin brothers live in Bogotá, a city of about 8 million people in the South American country of Colombia. One day in 2013, a woman takes a friend along to visit one of the twins, who works as a butcher.
Only the friend sees, in the butcher, an exact, living, breathing copy of one of her co-workers, Jorge. Even though the butcher insists, to her face, that he is not Jorge. His name is William.
Things only get weirder and more complicated from there. Back at work, the friend tells her co-worker, Jorge, about the strange encounter at the butcher shop. As it turns out, Jorge says, he already has a twin brother.
And so does William, the butcher.
Finally, there's this: The butcher's twin brother and the co-worker's twin brother also are dead ringers for each other.
It's the old tale of the hospital switch, in almost unbelievably real life. Two sets of identical twins were born in late December 1988, one set in Bogotá, the other in in rural Santander, north of the city. When one of the twins in Santander fell ill — all four were born prematurely — he and his twin were sent to the hospital in Bogotá.
Here's what happened from there: Instead of sending the boys home as they should have — let's pair them off as Twins 1-2 and Twins 3-4 — the hospital somehow got them mixed up and sent them home as 1-3 and 2-4. One set of twins ended up in Bogotá, the other in Santander.
The mix-up finally came to light when William and Jorge, pushed by their friends, met in a square one night in Bogotá. There was no mistaking it then. It was clear they were identical twins, meeting for the first time. They were 25.
The story is chronicled in The New York Times Magazine story, "The Mixed-Up Brothers of Bogotá," and a new book co-authored by psychologist Nancy Segal, "Accidental Brothers: The Story of Twins Exchanged at Birth and the Power of Nature and Nurture."
William Cañas Velasco, the butcher, grew up with who he thought was his fraternal twin, Wilber, in a small town in Santander.
Jorge Enrique Bernal Castro grew up with who he thought was his fraternal twin, Carlos Bernal Castro, in Bogotá.
But William and Jorge are the true, identical twins. As are Wilber and Carlos.
"I was scared, because there were two people who looked exactly like my brother and me, but at the same time, I didn't know who they were," Jorge told the BBC in 2016 about that first meeting.
The discovery was a gold mine for Segal, but it has done little to settle the nature vs. nurture debate.
"In many ways," Segal writes in the preface to the book, "the real identical twins in Colombia — Jorge and William, and Carlos and Wilber — aligned according to their genes. But while their similarities were striking, the parallel lines broke down in places, crisscrossing like streets on a Google road map."