On Saturday, April 26, without telling anyone his plans, Ralston packed his hiking boots, a hydration system, his backpack, climbing equipment, and, notably, a pocket-sized utility tool, put his mountain bike in the back of his truck and drove almost five hours to a remote part of Utah.
'I was accustomed to being in far, far riskier environments,’ he says. 'So I thought going into that canyon was a walk in the park – there were no avalanches, it was a beautiful day and I was essentially just walking.’
But suddenly, Ralston slipped and fell down the chasm, dislodging an 800lb (360kg) chockstone boulder, which is much harder than sandstone. It crushed his arm and left Ralston pinned against the canyon wall.
He made several futile attempts to chip away at the boulder with his utility knife – but it was already fairly blunt and this just made it worse. That first night, as darkness descended on the Utah canyonlands, Ralston realised just how alone he was.
I realised early on that I was going to have to cut my arm off to get free but there was also resistance: I didn’t want to do it,’ he says. 'But by the second day I was already figuring out how I could do it, so in the film you see that progression: trying to cut into the arm like a saw, finding the tourniquet, then the realisation that the knife was too dull to get through the bone. That despair was followed by a kind of peace; a realisation that I was going to die there and there was nothing I could do. It was no longer up to me. All I could do was see it through to the end.’
After five and a half days inside the canyon, out of water, delirious and hallucinating, Ralston had an epiphany. 'I felt my bone bend and I realised I could use the boulder to break it. It was like fireworks going off – I was going to get out of there.’