Tackling the unclimbed west face of the remote Siula Grande in the Andes, Joe Simpson and his partner Simon Yates achieved the summit before disaster struck. A few days later, an exhausted Simon staggered into base camp to tell their non-climbing companion that Joe was dead. For three days he wrestled with guilt as they prepared to return home. Then a cry in the night took them out, where they found Joe, badly injured, crawling through the snowstorm. Far from causing Joe's death, Simon had saved his friend's life when he was forced into the appalling decision to cut the rope.