It’s a crowded world we live in. Director Danny Boyle drives the point home from the moment 127 Hours opens, putting on screen clip after clip of writhing masses of humanity. So many people, in fact, that just one shot can’t hold them, and he begins subdividing the screen, doubling, tripling the loud, chaotic bustle (both of these elements — split screens and crowds — become separately recurring motifs as the film progresses). For the sake of convenience and society, we cram ourselves into small spaces, but often, for the sake of our sanity, we need to get away from those madding crowds. Aron Ralston was doing just that on a gorgeous late spring day in 2003, on a solo canyoneering trip in the deep, narrow slot canyons of eastern Utah.

It was in one of those slots that Ralston accidentally dislodged a boulder, sending it and himself falling down to the bottom of the crevice. In one of those freak moments in which things go wrong to an extremely precise and unlikely degree, the boulder lodged immovably in a narrow space between the canyon walls, with Ralston’s right forearm crushed and pinned between the boulder and one wall.

And so begins the titular 127 hours, the time Ralston spent there trying to escape, but waiting to die, with few supplies apart from a little water, a burrito, some climbing rope and a cheap multi-tool with a blade too dull to even break the skin.