How did a beautiful girl grow up with loving parents and have so little in common with them not their looks or skills and that's just the start of a mystery, now being solved and all leading back to a... See More
How did a beautiful girl grow up with loving parents and have so little in common with them not their looks or skills and that's just the start of a mystery, now being solved and all leading back to a strange man in a fertility clinic. A man who could have deceived hundreds of families in the worst possible way. Here's Cecilia Vega. Reporter: It started off as a hobby -- researching family history. So it gets addictive? Yes, and boy, did I get bit by the bug. Reporter: But what Pam branum uncovered would reveal an unthinkable secret about her 21-year-old daughter -- it involves a fertility clinic and a monster unleashed from the grave. It shakes your world, absolutely, because everything that you knew to be true, all of a sudden wasn't. You know, you're like, pinching yourself, going, "This is the worst dream I have ever had. I am gonna wake up." And it didn't happen. Reporter: It happened. It happened. Reporter: It happened in salt Lake City. Newlyweds John and Pam branum are trying to start a family with no success. So, as a last resort they go to a fertility clinic here on the campus of the university of Utah. A friendly lab technician shows them a photo collage above his desk, of babies conceived by artificial insemination. And, you know, I just looked at those pictures and I thought, "This is gonna be it!" Maybe this is gonna happen for us. Reporter: But something about the lab tech doesn't sit right with John. I remember handing him the sperm specimen and he gave me this, just sort of evil smile. It just made the hair on the back of my neck stand up. I thought, "Whoa!" Reporter: John's reaction is soon forgotten, though, with the arrival nine months later of a beautiful baby girl, Annie. Reporter: Flash through the years and the memories. She's musically-inclined, and we always kind of wondered where that came from. Reporter: Annie grows into a beautiful, bright young woman, a college whiz-kid who studies astrophysics and surprises her parents with her gift for math. I barely made it through calculus 1. Well, in Annie's second year of college she was doing calculus 3, making As, and I'm thinking there's a recessive gene at work there, right? Reporter: With her nest now empty, Pam picks up a hobby and gets hooked on researching the family tree. She would be up to 2:00 to 3:00 in the morning doing this. Reporter: These days anyone can stick a swab inside their cheek, go online, and for a few bucks, discover relatives and health histories they never knew they had. Pam branum swabbed the whole family. I thought it was really interesting how it tells you about your health. It tells you where you come from. Reporter: As expected, when the results come back, Pam finds that Annie shares 50% of her mom's DNA. But what about her dad? And it said that they shared zero DNA. I was in a panic. You know, I was in a complete panic. Annie walked through the door, didn't say a word, gave me a big hug, started sobbing. I think it took a very long time for it to sink in. Reporter: What was it that sunk in? Trying to comprehend what it meant that he wasn't my biological father. And then, who is? Reporter: The branums says for months they couldn't get answers from the university. It would take a DNA detective to get to the bottom of it. They wanted to know what her biological heritage was on her paternal side. And I'm well known for doing that. Reporter: Finding biological fathers is a specialty of cece Moore, a genetic genealogist in southern California. Desperate for answers Pam sends her an e-mail. This is right up my alley. Reporter: She tells Pam to send Annie's DNA to multiple online DNA databases. And in this type of work, we always say if we can find a second cousin, or a predicted second cousin, we're pretty much in business. We can usually solve the case. Reporter:: Moore's hunch pays off and the plot thickens with a single match between Annie's DNA and this total stranger in Minnesota, Carla Evans. What this retired school secretary knows will blow open the whole story. She asked me if I had a relative that might have donated sperm. And, I said, "Yes, I did." And I said, "Well, can you tell me where he, he lives?" I said "Well, he lived in Salt Lake City a lot, and I know he used to work for a fertility clinic there." And I thought, "Well, okay. That's it." Reporter: That relative was Carla's cousin, Tom Lippert. Pam and Carla exchange photos and suddenly pieces of the puzzle start falling into place. When I first saw Annie's graduation picture -- it looks almost identical to Tom's graduation picture. When I saw that photo, I just knew that Tom was the father. Reporter: She also recalls some things that might explain Annie's interest in music and her college ambitions. Well, Tom was very talented. He was very intelligent. He went to notre dame law school. He was also musical. And I looked at those pictures and I recognized him. Reporter: You recognized him? He was the man at the clinic. I could picture all those baby pictures behind him, the ones that he was so proud of. He had made a big deal out of the fact that, "These were all of the families that I've helped conceive." Reporter: This is so creepy! Picturing him sitting next to that wall, is chilling. And I just thought to myself, "This wasn't a mistake. This was done intentionally." Reporter:: But the story dead-ends in a cemetery. Tom Lippert died in 1999. Case closed until, that is, Carla Evans drops a bombshell. She said "Pam, there's something I need to tell you and I want to be totally up front with you about whom my cousin was. Tom kidnapped this young woman from Purdue university. Reporter: That's right. Tom Lippert was a convict. A kidnapper who gained national attention in 1975, sentenced six years in prison for abducting a young woman. The details would unhinge everyone. He held her for three weeks, sometimes in a metal studded box. For me, that was as devastating as finding out. Reporter: After getting out of prison, Lippert married a quiet Salt Lake neighborhood. He terrorized the neighbor kids. We were so scared. We would walk on the other side of the road. Reporter: Tessa Murdoch says Lippert threw rocks, broke windows and even made the local news. Did you throw rocks? Absolutely not! I never knew why he hated kids so much. Reporter:: Ironic, because hating kids didn't stop him from conceiving them. Swapping his sperm for that of patients while working as a lab tech in the fertility clinic at the university of Utah. At the time, the clinic did not do criminal background checks on prospective employees. We are deeply sorry for any anxiety this has caused our patients. Reporter: Finally, this week the university admitted that many lab records were destroyed. They can only guess how many sperm samples were handled, or mishandled, by Tom Lippert. Cases could soon be coming out of the woodwork. I would say thousands, that's an estimate. Of people who might be affected. Reporter: DNA detective cece Moore created a blog that's already gotten responses from at least 5 more possible Lippert offspring who'd be Annie's half-siblings. You think there are other families out there right now, who were duped just like you? I know it. I know it without a doubt. I wouldn't wish this on any other family. Reporter: Still, the branums know their turmoil is far outweighed by the one beautiful blessing that came out of it -- their daughter Annie. What have you learned? About yourself. About your family? That we're just the same. My dad is my dad, regardless of whether or not he's biologically related to me. He's the one who raised me.
This transcript has been automatically generated and may not be 100% accurate.