Dean Potter is the only person in the world who does extreme slack-lining. This hair-raising variation of tightrope-walking finds Dean high in the sky, crossing a bouncy, one-inch-thick stretch of rope without using either a pole for balance, or any kind of safety harness. Dean has 'slack-lined' across some of the world's most breathtaking canyons, suspended hundreds of feet above the ground. One slip could see him plunge to his death. This nail-biting film follows Dean as he prepares for his bid to complete the longest high-line crossing ever, and, by doing so, cement his reputation as one of extreme sport's greats.