On June 3rd 2017, professional climber Mark Synnott was in Yosemite to witness something that only a handful of people knew was about to occur: his friend, Alex Honnold, was going to attempt to summit one of the world's most challenging ascents, a route called Freerider on the notorious rock formation El Capitan. It is an extraordinarily dangerous and difficult climb, and yet Alex was going to do it 'free solo'. Meaning no help. No partner. No equipment. No rope. Where a single small mistake would mean certain death. Indeed, to summit El Cap free solo was a feat likened to Neil Armstrong first walking on the moon. As Alex plots, rehearses and ultimately attempts his heart-stopping ascent, Mark also shares his own personal history of climbing, filled with triumphs, defeats and dilemmas, in this deeply reported, inspiring exhortation to live life to the fullest.