Transcript for Wallenda's NYC high-wire walk faces complications
Now to an ABC news exclusive. The race to get ready for that death-defying stunt above times square. Last night NIK Wall Street and his team worked on it and it proved to be more challenging than they ever imagined. T.J. Holmes is outside with more details. I thought we would see you up on the wire. You know me better than that. There's always the hustle and bustle going on. All the busy moments, if they would look up, you see a wire above times square. All the action on the ground usually but plenty of action above because not just one but two people are going to walk that titlerope through times square, no safety harness, no net. The clock is ticking days before the wallendas will attempt to walk a wire between two high-rises above times square. Rigging that wire that NIK Wallenda and his sister lijana will cross came with unexpected difficulties. You don't know what's going to happen. Reporter: The executive producer of Sunday fight's show tells us installing the wire this week proved more thalg challenging than NIK ever imagined and that NIK's team will be making adjustments to it all week because there is zero room for error. They have been training for the worst possible conditions using wind machines and preparing for torrential downpours using hoses blasting water. Only lightning or strong winds could thwart their event. Nothing compares to this. Reporter: The stunt is the first time the brother/sister team will perform together live since 2017 when lijana and four others were severely injured falling 0 of a high-wire while rehearsing to break a guinness world record. I broke a rib, punctured my right ear canal. Broke near through my left humorous. I broke my left Cal canous but the bin one was every bone in my face. Reporter: She is still dealing with nerves, just days before one of the biggest challenges of her life. How are you feeling? I'm a little nervous because the wire moves more than anything I've been on. Reporter: There will be a tricky part where they come together and have to cross each other in the middle of the high-wire and heard from ginger about the weather on Sunday for the ee haven't. Should be fine, no high winds or heavy rain even though they prepared for the worst. You heard lijana say she's nervous. How about you? I'm nervous as well. Join me and eri. For this event called "Highwire live in times square with NIK Wallenda."
This transcript has been automatically generated and may not be 100% accurate.