Tonight we are going to take you inside an extraordinary competition, one that tests the limits of animals and humans. The rules are simple. Adopt a wild horse and in four months make that horse tame... See More
Tonight we are going to take you inside an extraordinary competition, one that tests the limits of animals and humans. The rules are simple. Adopt a wild horse and in four months make that horse tame enough to perform in a show. One with a million dollars up for grabs. As you are about to see some of the people involved in this contest are a bit on the wild side themselves. Here's abc's juju chang. ♪ Reporter: The final round of the mustang million competition and much more on the line than bragging rights. Fort hood, texas are you ready to get it started on a saturday night. Let's do it. Reporter: At stake a million dollars in prize money. 190 cowboys and cowgirls from across the country compete in the fort worth, texas arena to show just how tame their once wild mustangs are now. But the real competition begins four months earlier. When these wild mustangs are auctioned with one goal. 120 days to turn them into winners. I'm looking for a nice fat ge lding. Reporter: Where we met bobby kerr, wife susan and daughter kelsey. You ready? I'm ready, you ready. Let's go get mustangs. Reporter: They adopt three wild horses to be trained and ready to compete. I am not even pulling on this horse. He is coming right around me. Bobby won last year. His horse, poncho, transformed into a meek, charming side kick, performing in the back of a southern vintage car. We started it up and drove off with him sitting in there. That's what makes this show so unique. Now bobby is trying to show he can do it again. Four months off 'round-the-clock training to see if trigger has what it takes. I'm using this to build his confidence. On where to put his feet. Turns out breaking a horse is not about brute force but gentle persuas persuasion. And occasionally it is the horse that seems to tame the trainer. Whoo-hoo. Seemed to take that well. Reporter: Bobby's land is in foreclosure, the former trucker's business hurt by the bad economy. If it breaks and we make the finals. It ruins the routine. I understand that. Little worried. Last year you took the prize money. The prize money means a lot to you. Yeah, yeah, a lot of people are here like me. But you know for the love of the mustang, and for the experience. This is how we make our living. It's, you know, a little over four months getting here. Other than my sponsor money i haven't had no income. Like betting the farm? Yeah, yeah. It's a big bet. Reporter: With a month to go before the competition it is clear bobby is still training a wild horse. Trying hard to get trigger to follow directions. You know if this doesn't work, we are in a big bind. To win $200,000 of the million dollars in prize money. Bobby feels he needs to pull out a show stopper. Must be hard defending your title. This is my third one. You got to get pretty creative. Trying to top yourself. Trying to top myself. Heap adding to the pressure training a first time c competitor. His daughter, kelsey. A different horse, the first night he got here. How different. Nervous wreck? Yeah. Were you a nervous wreck? Reporter: Before taking on the challenge. Kelsey considered herself a party girl than a cowgirl. I want to school. I lack ike to party, go to the bars, sleep in. We brought a wild horse. Pretty much a wild girl together. And -- they both changed just incredibly. I mean they have done a total flip. Both the horse and her. Reporter: Kelsey slopely trains her horse drifter to follow her every lead. The mustang millionaire, showcases the annual competition designed to to get more people to adopt wild horses. The will rodgers arena, a packed house, 5,000 people await the final showdown. It's competition day. Kelsey doesn't qualify for the main event this year. But her father does. And it's now time to find out if this extreme mustang makeover worked. And bobby faces intense competition. As we get rolling into our top 20. Our first competitor will be -- bobby kerr. I think a lot of people are, expecting, wondering, what I am going to dupe this year. I told him I came here for one show. The champ. Re-created a scene from the movie tombstone. He built this giant water fall so his horse trigger would jump through it. And take the horse. A few months ago. I mean that's quite an accomplishment. This is where 120 days were with of exercises designed to to build trust and keep the horses from being spooked will hopefully pay off. Who is ready to find out how it shakes loose. We're done to the last three horses. You want them to be the last one picked of course. So it's quite a bit of suspense. And your third place individual, we congratulate, jingle bob, shown by bobby kerr. It's not to be. Bobby suffers a stunning upset. I had good routines. Happy with my horse. I was already happy. When they called me up for third. I was real happy. Neither of his horses win. Yet he managed to bring home, $160,000 in the prize money. The winning horse's journey started 3,000 miles away and is very different than that of bobby's. Hard work. Hard work. Reporter: But the endless hours of training reaped a different kind of reward. He has always been my hero. You know, there is nothing better than getting approval from your family. You know? That's when you really feel like a winner. And if your kids think this is cool, that, that really makes it worthwhile. You got a little lump in your throat don't you? Little bit. Reporter: What explains that? I love my girl. I'm proud of her. Reporter: For "nightline," juj u chang in fort worth, texas.
This transcript has been automatically generated and may not be 100% accurate.