as a researcher, she had made a home visit to sharon morello when she was a little girl. d for the home visit, however, she realized she knew sharon's adoptive mother, vivian. they had met in college. still, even with that personal connection, janet kept the secret. janet got out of her car that day, and went inside that house and studied that family and that twin and never told that her baby was an identical twin. >> no. >> wow. more than 40 years after janet and other researchers studied sharon, the former research assistant agreed to meet sharon and her mother. and you might remember this woman, professional people finder and abc news consultant pam slaton. pam first brought the story to "20/20's" attention. >> janet. hi, i'm sharon. >> nice to see you. >> yes. >> i was a research assistant on the study that sharon was in, and vivian and i actually went to college together. one of those small world, incredible coincidences. >> but if janet expected a happy reunion, that's not what happened. things quickly get tense. >> you knew that she was a twin. >> yeah. >> and you n