our searcher, pam slaton, and abc news korean bureau chief joohee cho, who has just arrived in new york after a 14-hour flight. >> i'm joohee. >> i know you are. nice to meet you. you did a lot. you were the key that unlocked the door. >> reporter: they've been working together on opposite sides of the world for several months. and now they're about the crack the case. after combing through countless false leads and phone numbers, pam finds one that rings true. she finds a number for a man in missouri named timothy james parker. pam believes he could be allen's long-lost son. he's not home when she calls, but a roommate answers. >> and i said, "well, is he by he said, "oh yeah, he is." i said, "oh," i said, um, "is he a twin?" he says, "yeah." i said, "he has a twin sister named" -- he says, "yeah, susan." i was like, "oh, my gosh." i mean -- >> reporter: you did it. >> i had to contain myself. >> reporter: now pam has a name for the female twin, named sandra when she was born in korea. she is now susan -- living in wisconsin. >> now, i jump on the computer. i run, "susan parker." boom.

>> reporter: abc seoul bureau chief joohee cho says jame and his wife believe connie regretted giving the twins up for adoption. it seems to have haunted her until the day she died. >> she would just go to anyone in the neighborhood and say, "if you see any twins, korean-american twins, looking for mrs. pae, that's me, that's me. make sure that they call me." and she would just look over the photo albums, and her daughter-in-law said she'd just cry and just touch the photos. ginseng box. it's a tin time capsule stuffed with mementos of a life that might have been. snapshots of connie. letters from allen. and look at this, the savings bonds allen sent all those years ago. she had saved them all her life. is it possible she planned to give this modest inheritance to her twins one day when they returned? if so, that day never came. allen's facebook page is percolating tonight. hundreds of well-wishers "like" the news of the big reunion. >> this is the best news ever. amazing! so glad for you all. so, so wonderful. so overjoyed. it's good to see him reunited with his children. i hope that

in seoul, south korea, abc news buau chief joohee cho helps us pull back the curtain on the four-decade mystery. her first stop, a meeting with mr. lee. >> translator: the most important thing for us is to figureut the mother's identity. >> reporter: almost immediately, a breakthrough. lee finds the twins' mother allen's ex-wife connie, she is listed in the korean government registry. >> she gave birth to twins. and, um, also she was married to allen thomas. so we're like, "bingo! yay." >> reporter: but the registry says connie died in 2007. so joohee's next stop on the advice of mr. lee is korea social service, a small adoption agency. joohee mentions connie's korean name to the woman at the agency. >> when i told her the name of pae seong-eun, and she had twins and, you know, there was this whole story on facebook, i got a eling that she knew who i was talking about, but she wouldn't admit it. >> reporter: the agency tells r allen has no right to access the adoption records, but there is someone who does. >> she said, "only siblings have rights to ask for it." she gavee that hint. it

>> reporter: abc seoul bureau chief joohee cho says jame and his wife believe connie regretted giving the twins up for adoption. it seems to have haunted her until the day she died. >> she would just go to anyone in the neighborhood and say, "if you see any twins, korean-american twins, looking for mrs. pae, that's me, that's me. make sure that they call me." and she would just look over the photo albums, and her daughter-in-law said she'd just cry and just touch the photos. ginseng box. it's a tin time capsule stuffed with mementos of a life that might have been. snapshots of connie. letters from allen. and look at this, the savings bonds allen sent all those years ago. she had saved them all her life. is it possible she planned to give this modest inheritance to her twins one day when they returned?