Transcript for Utah doctor's lies revealed after investigation into wife's death: Part 1
Michelle Summers, she's gorgeous. She's just beautiful on the inside and out. Very graceful and classy and Michelle was 21 years old when she met martin Mcneill, and within months they elope and got married and began a family. Very quickly. Boom, boom, boom. They adopt children from Ukraine. And that's it off in the distance. And the family grew to not just four children but eight. Martin Mcneill was appointed by the governor of Utah to head up a very large medical facility. He walked in the room and sort of took it over like he was above everybody. We did try to warn her. He had total control. When my father turned 50, he started acting very strangely. He became just very obsessed with losing weight and his appearance. How did your mom react? She was suspicious. Michelle became very suspicious and confided in her daughter Alexis she thought her father was having an affair. Michelle confronted martin Mcneill with allegations of an affair. And ever the manipulator, he turned the tables on her, martin Mcneill convinced her she needed a full-on face-lift. She was afraid she was losing her husband. Martin found a plastic surgeon and came in with a list of things that he wanted Michelle to have. Michelle ended being pea described percocet, lortab, valium, aim been, phenergan. He wanted his wife to go home with lots of prescriptions for sedatives and painkillers. The surgeon deferred to Dr. Mcneill because he was going to take care of his wife personally. Reporter: When she came out of surgery, how did she look? She looked bad. Reporter: The next morning when you saw your mom she was heavily medicated. She was completely completely sedated and out of it. He gave her more medicine. I said no, I'll take over. She started to cry. She said if anything happens to me, make sure it's not your dad. I kind of got upset. Reporter: The night before Alexis went back to medical school, Alexis said her mom looked great. He went into work as normal, picked up Ada from school and arrived at the house around 11:35. She ran in calling "Mommy, mommy." My dad stayed in the kitchen while she went into the bathroom and found her. And then she screamed for my dad. Fallen in the bathtub! She is unconscious. She's under water! I need help! They're on their way! Is your wife breathing? She is not. I am a physician. Reporter: Martin Mcneill decided to call his daughter Alexis. She's in the tub, she's not breathing, I called an ambulance and he hung up. And I was just screaming, he killed her, that was my first instinct, he killed her. She said dad murdered mom. Reporter: Martin has had somebody flush all of Michelle's medication down the toilet. As soon as I heard that, things are starting to add up. My mom was concerned, because rather than spending more time at home he's spending more and more time away at the office. While he was sleeping, I printed out all of his phone records, and we found this number that he'd been calling a lot, gypsy Jillian Willis. Reporter: Gypsy Jillian Willis was a woman that martin Mcneill had met online. Did you know he was married? I did. My father demanded that we have a funeral within just a couple of days. Among the crowd was gypsy Jillian Willis. Reporter: You crashed her funeral? I had felt sorry that I had been involved with martin inappropriately. We'd come to find out that my dad had been dating gypsy for several years before my mom's death. Martin had a set plan right away. He was going to hire a nanny. And he said there is going to be an interview for a nanny, and that was gypsy. Gypsy. Reporter: Why did she move into the home? Martin said he needed help with his younger children. Reporter: Were you still sleeping with him? I was. Reporter: So were you the nanny or the girlfriend? I had moved in to help with the kids. When we had opportunity, I still slept with him. Reporter: So you were both. She walked into the house like she owned the place. And then when I questioned my dad, and he said oh, she's a guest in the home. He wanted to make it known that it was either gypsy or his children, and he chose the Reporter: You must have been shocked when three months after she died he proposed marriage to I wasn't shocked. Seemed like a natural progression. I believe he did love his wife. He mourned Michelle, but she was gone, and I didn't suspect anything unusual. Police didn't really conduct much of an investigation at all. They didn't collect any of the evidence, closed the book on this case and ruled it a natural death. Reporter: Michelle's daughters were absolutely outraged that the police closed the case so quickly on Michelle's death. And Alexis and Rachel and Michelle's sister began their own investigation. We said, you know, we have this new information. We know about a girlfriend now. They took no notes. They acted like we were out of our minds. In talking with the investigator there in pleasant grove, they felt like this was all a natural cause kind of thing. Could they have done more? They could have. But I think the initial response was appropriate. Doug Whitney and Jeff Robinson were two people with the prosecutor's office, and they were assigned just to work special cases. I got information from the daughters and got enough to get an investigative subpoena. Reporter: Doug Whitney began investigating everything he did and uncovered a life of lies. When he was in his early 20s, he went to jail for check kiting. He was charged with forgery, fraud. Okay, I'm going to take a picture. We basically found out our entire lives had been based and surrounded on lies. That everything about our experience with our father was a lie. You played a part in destroying our whole family, dad. I am the victim, I am the victim. My logic is I didn't commit adultery. I didn't kill your mother, I didn't have a mistress. I don't have one now. Whether you want to accept it or not, I've done nothing wrong. Reporter: Michelle Mcneill adopted four girls. And I saw this little girl, and I said I have to have her. Look on the computer when she's 8, and I said I've got to have Reporter: Elle, Ada, Sabrina and Gisele. Gisele was the oldest adopted family member. A few months after Michelle's death, he decided to send Gisele back to the Ukraine for the summer. He sent Gisele back home to the Ukraine for two months, but then those two months began vetching into almost a year. The rest of the family couldn't understand why Gisele didn't come home. Little did they know that Mcneill and gypsy Willis had taken Gisele's social security number. Gypsy Willis assumed Gisele's identity. Reporter: How did this idea come up? When I got together with martin, I had a lot of tax debts, probably in the range of $50,000 or $60,000. This was martin, this was martin's idea. This was martin's activity. Reporter: Why did you do it? I said I didn't want to. He said this is the best way to do it. Reporter: You got three joint bank accounts using a fake name, a fake birth certificate, a fake Utah state I.D. Card and a fake social security card. How can you be a passive participant in that? He was very powerful and influential. I just assumed he knew what he was doing. Gisele had no idea what was going on. She set plans in motion right away to bring her back. Her last day in Ukraine! Thank goodness, she's excited. Reporter: What the family didn't know was this incredibly passionate move to bring her home would put a total wrench in all of martin's plans. Now there's two people with that social security number and that name. Martin and gypsy were both arrested and sentenced to separate prisons where they served time for the identity theft. Reporter: Martin is gone but not forever. He's only behind bars for four years, so the family knows he'll be out eventually and leaves time to wonder what else is martin Mcneill capable of doing. Investigators became convinced martin killed Michelle because he wanted to be with gypsy. "Nightne," the perfect nanny, will continue.
This transcript has been automatically generated and may not be 100% accurate.