What happens, 28 years after an accidental maternity-ward switch, when identical sisters meet each other?

A Spanish mother gave birth to twin girls in 1973 at a hospital in Las Palmas, Canary Islands, but one of the babies was accidentally switched in the maternity unit. The mistake went undiscovered for nearly three decades. The mother assumed that she had given birth to fraternal twins (dizygotic, from two eggs) and not "identical" ones (monozygotic, two embryos developed from a single fertilized egg). The girl she named Begoña was her biological daughter; the baby named Beatriz was not.

As Nancy L. Segal relates in "Someone Else's Twin," her fascinating account of the switched-at-birth misstep and the painful family and legal entanglements that followed much later, an unexpected encounter in a clothing store was the tale's turning point. A shop assistant mistook the 28-year-old Begoña for a person she knew named Delia. After Begoña explained who she was, the clerk—still struck by the resemblance—suggested that the two "doubles" meet each other.........