Transcript for Inside Nik and Lijana Wallenda's training for their Times Square high-wire walk
Reporter: The whole world knows times square. You make it New York can you make it anywhere. This weekend, high above the center of the world, NIK Wallenda will attempt to make history again. Alongside his sister and fellow daredevil Leanna. They will walk on a wire over times square in New York City. 1300 feet on a cable no thicker than a garden hose, hanging for more than 250 feet above the Earth. To do something that's literally going to leave my finger print on the city is pretty exciting. Reporter: A come back for the gravity-defying siblings, just two years after a horrifying fall that changed their lives. It is permanently instilled in your brain, imprinted in your brain. You can't make it go away. In it was a miracle that Leanna's alive. Reporter: That come back happening with the entire world watching. The analogy of getting back on the horse. For us it's about getting back on the wire. It's a guy walking on a cable. We can all relate to walking. Reporter: Walking, yes, but walking where birds fly. For NIK Wallenda, it isn't simply where he makes his living, his life, a chapel in the sky. A wire walker defying death is in his blood. One wrong step means certain doom. It's what we were born to do, what we love. Reporter: Whether teetering on the edge of the grand canyon, walking blindfolded along the Chicago skyline. His 26th minute of the walk. Sprinting to the finish! Reporter: This matters a great deal to you and the family. Wallenda became an international phenomenon in New York. My family's first performance in the United States was in 1928 in Madison square garden in new York City. Reporter: The Wallenda family known famously as the flying wallendas trace their roots to European circus performers all the way back to the 1700s. Challenging death in their DNA. A showcase in this 1963 documentary for the cbc. They are seventh generation wire walkers. Their family has been performing mesmerizing feats of athleticism for decades. My mom was walking the wire when she was six months pregnant with me. For me being on the wire is alive. There's something extremely serene and peaceful. Some find peace by going on a jog or reading. Reporter: But in that peace there is the constant risk. The family has not been immune to the danger. Several wallendas have died or been injured in high wire falls. In 1978, NIK's great-grandfather fell to his death in Puerto Rico at 73 years old. This video skap toured by a local news team showing his final harrowing moments. It's a terrifying truth NIK and Leanna know all too well. Take me back to 2017. It was February 8th, about 10:30 in the morning. As we made our way out on that wire we lost our balance and the pyramid collapsed. By the grace of god I caught the wire. My cousin caught the wire. Another gentleman stayed on the wire but five of my family members and friends hit the ground. I broke a rib, punctured my right ear canal, broke through my left humerus. But the big one was every bone in my face. The trauma doctor said when we first got the call, he said the fear in the voices of the paramedics, he said I was certain we were going to have fatalities by the time they got to the hospital. But ten days later, Leanna's going home, so. Reporter: To this day, the family has agreed not to watch the video of the fall. It's just hard to relive it over and over again. It's weird when something that dramatic happens to you. Every single step of the way, I mean, that's why I'm emotional because I'm there again. Falling from over 28 feet, the reality is I think it's a 60% chance of living. People say why would you return performing? It's your passion, it's what we we live by the words never give up as a family. And we have for generations. There's something about closure, about getting back on that wire. I know my sister for a year as she was recovering struggled, because she wanted to get back on the wire. She wanted to close the circle left open by the accident. I'm a little nervous because the wire moves more than anything I've been on. Reporter: At their practice facility in Florida the weight of being on the wire is palpable on Leanna's face, but she works through it one step at a time. She has had to overcome hurdles. I knew I'd get back on the wire. Reporter: The wallendas have set up a massive practice wire, 50 feet high and 500 feet across, which they practice on daily. Trying to mimic what they will face on the day of the walk, preparing their bodies and their minds for the lights and sounds of New York City. I'm looking down and trying to visualize those light-up signs flashing. Taxicabs moving, horns honking, police, sirens, all that. And then there's a lot of training. Reporter: High above the ground the two will walk towards each other, meeting smack-dab in the middle. The most dangerous part of the performance where NIK will step over Leanna before they continue the rest of the way. But while the physical training prepares them for life on the wire their warrior ethos is rooted in a higher power. Reporter: You mentioned praying. Like over niagara falls and it was like going to a church service. Praise you Jesus. My faith plays a huge role in who I am. And people ask how you stay calm and collected in stressful situations and the reality is by my faith. I have a lord and savior that's looking out for me. And I know he's there with me. I will say this. I have to make the right decisions in training and preparation. I don't believe god holds me magically on that wire. Can he? Absolutely. I don't believe he does. It's up to me to use my mind, knowledge and experience to train and prepare properly for every walk I take. Reporter: They have spent days laying down hooks and wires. Everything overseen by NIK and his family. The rigging has everything to do with success or failure. It has to be absolutely right. In terms of difficulty, this is probably the worst case that I've been up against. There's been nothing like this. Reporter: While NIK and Leanna will be wearing a safety line during their walk, their lives ultimately depend on just a few hooks and cable. I'm so blessed to have an opportunity to hopefully inspire people that because NIK Wallenda can make it across the grand canyon or niagara falls with his sister, if they're able to do it, so can I. Reporter: You have a wonderful family. You've had a terrific career. Why -- Ask Tiger Woods why he golfs. Same reason. It's my passion. It's my love. Reporter: If Tiger Woods misses a shot, the worst that happens is he misses a shot. The reality is when it's your time, it's your time. A lot of people hold back from their dreams because of fear. Fear is a liar. It holds you back from your greatest successes in life. I encourage people, do not accept the fear put in your mind. Overcome that fear.
This transcript has been automatically generated and may not be 100% accurate.