Transcript for Broke Woman Goes Undercover to Get Money from Ex
Announcer: "20/20," how far would you go continues. Once again, Elizabeth vargas. Reporter: It took six long years, but Katherine Underwood realizes her mistake. She's bankrolled the dreams of budimir Drakulic. In return, she got an empty promise and an empty bank account. I felt stupid. Reporter: Katherine decides to go on the offensive. She's begins to take a closer look at budimir and his story has some holes in it. First at ucla. I found out he had left ucla in October of 1993. He was not a professor at ucla. Reporter: And what about all those late nights working at Edwards air force base? Katherine says a late night phone call in 2000, woke her up in more ways than one. I looked at the caller I.D. -- Mm-hmm. -- And it was a Los Angeles number. He wasn't calling you from the desert? No. Well, then I knew I was in big trouble. Reporter: The next day, a devastated Katherine flies to L.A unannounced. She recalls the time budimir first showed her around the ucla campus and him talking about playing tennis. So, grasping at straws, she heads to the tennis courts. He was playing tennis. He was taking a tennis lesson. So in that moment, when you saw him on the tennis court, reality slapped you in the face? It sure did. Hard. He was a liar. That's the worst. Reporter: Did you come front him? Yes. He was very ugly and very nasty. He wanted me to leave and asked me that I had no business coming to Los Angeles unannounced. Reporter: From the tennis court, Katherine goes to superior court and files a lawsuit and wins a judgment. The judge called budimir's conduct "Willful, malicious and despicable." At the time, Katherine was awarded more than $800,000. Today, with interest, that figure has ballooned to more than $1.6 million. Budimir has appealed twice and lost twice. Truth be told, he didn't look all worried when we spotted him at his private "Members only" gym. A lot of people would think, "Wait a second, you have promissory notes showing you lent him this money, you have a court order ordering him to pay you back this money -- Yes. Why can't you get the money back?" He had a team of attorneys. Reporter: Katherine can't afford a team of attorneys. So, Underwood goes undercover with a series of low tech getups designed to get her close enough to actually hear things and see things that hopefully will lead her to her money. Tracking budimir becomes Katherine's obsession. She follows him to business meetings, stores, banks. You dated this man for six years. He never noticed or recognized you? I worked hard to disguise myself. Reporter: At one restaurant, the former couple gets seated a little too close for comfort. The waiter came up to ask me for my order, and I couldn't talk to him. You were afraid he would recognize your voice. The voice he would recognize. Reporter: At that meal, Katherine listens as budimir brags to a co-worker. I heard him say that they had outsmarted us. Reporter: Katherine's one-woman investigative unit is generating some leads but she can't even cover her own hotel expenses. So where did you stay? Ashamed to say -- It's okay. I'd sleep in the car. In the car? Reporter: The economic burden is being felt -- not just by Katherine, but by the brothers who came to her rescue. My brother was borrowing against his home. He what? He borrowed money against his home. Against his home. I just felt like the whole time I was out there I had to -- I had to get my money back. Reporter: We pay a visit to budimir's home. I'm looking for budimir. I'm Elizabeth vargas from ABC news. A male voice on the other side of the door asks what we want. For Katherine Underwood, the answer is simple -- $1.6 million and some closure. Budimir, you should be ashamed of yourself. You're living a nice life out here in L.A. And you took my money and look at you. 11:00, you're not even at work. I want my money back. You took my money and my brother's money and I want you to return it. Enough is enough and I want to be paid back. Reporter: The plea is met with silence. Once again, Katherine walks away empty-handed. To level the playing field for Katherine, we enlisted the help of two heavy hitters. First, Nelson tucker who walks softly and carries a big badge. Let's just say he's got a certain way of making people pay up. And bob Nygaard, a street smart private eye who has appeared on "20/20" before busting scams. She was conned out of a lot of money and she deserves to get that money back. That's the bottom line. Reporter: The P.I. Does some digging and uncovers a disturbing detail. Even as Drakulic was borrowing money from Katherine back in the '90s, he was eng $180,000 a year at a tech company in California. Talk about adding insult to injury. It really is a travesty of justice. Reporter: Nygaard makes a very good living playing his own version of hide and seek. So, here he comes. Coming out now with his food. Reporter: On this day, he's tailing Drakulic to see where he works. That question is answered when budimir pulls into biosig technologies. You have budimir working for biosig, collection a salary and you have Katherine not collecting any of that money. That's wrong. That's just flat out wrong. Reporter: And as the private eye learns, budimir doesn't work cheap. His total compensation in salary and stock at biosig for the past 3 years totals more than $1 million. But, on paper, he is a phantom who appears to have no assets. Yes, I was amazed that he was making this kind of money and not doing something to try to settle the case and have it go away. Reporter: Nelson tucker is a process server extraordinaire who has served papers on everyone from celebrities to heads of state. Today, he's going to biosig not to serve budimir but to serve the company that pays budimir in an attempt to garnish his wages. Do you know budimir Drakulic? Yes, he works with us but for some reason he's not here today. Is he normally here? Yes. It's very important the company does not disregard this order. This is a court order and a file has been opened with the county sheriff, and so if you fail to comply with this order -- you meaning the company -- there are repercussions. I understand. Reporter: So now budimir -- unmasked to his company and to the world -- must move quickly. If he fails to respond to the court order by next week, biosig must legally deduct 25% of his income and send it to the L.A. Sheriff's office for Katherine. But until that money is in her bank Katherine Underwood is not celebrating. She's come too far and waited too long. He could've given me my money back at any time, and I would've walked away and never looked back. He put me on a waiting game for all of those years. And he let me wait, and wait. Where's my money? Show her the money. We'll see if he does. So, how far would you go to get back money from an ex? We're live tweeting tonight so let us know using #abc2020. Next -- how far would you
This transcript has been automatically generated and may not be 100% accurate.