In late April 2003, hiker Aron Ralston was trekking through a canyon in southeast Utah when an 800-pound boulder shifted and pinned his right arm. Inextricably stuck, alone for five and a half days, armed only with a bottle of water and a few burritos, he became hypothermic and dehydrated and slipped into visions and despair. Finally, in a last desperate attempt, he severed his own arm. Then, dripping blood all the way, he rappelled 60 feet and walked eight miles to rescue. “Hero” is too weak a word.