Mountain-climbing-disaster documentaries are irresistible for a mountain of reasons, not least of which is that we can watch from a safe, flat remove and cluck, ''What were they thinking?'' Short of those escaping political persecution, aren't the men and women drawn to extreme mountain challenges creators of their own adversities? And if they are, does overcoming those adversities make them role models of bravery in the face of hardship -- or marvelous, headstrong fools with missing noses and limbs? Touching the Void, a daring half-dramatized, half-documentary film adaptation of the best-selling book by Joe Simpson about a catastrophic 1985 climb of Peru's 21,000-foot Siula Grande mountain by Simpson and his climbing partner, Simon Yates, manages to convey both sides of the slope at once.
The two Brits survived, we know that: 17 years later in a London studio, they narrate the story of their successful ascent and terrible descent, during which Simpson fell and broke his leg and needed to be lowered by rope down the mountain face in agony, 150 feet at a time -- a challenge that turned out to be only the start of their ordeal. At one possible life-and-death juncture, Yates had to decide whether to cut the rope attaching him to his unresponsive partner and save himself. Articulate, intense, and framed in talking-head intimacy, Simpson and Yates vividly describe the accumulating horrors, with Richard Hawking, a far less experienced climber they met on the way, providing a kind of dolts-like-us chorus. (He spent his time in their base-camp tent thinking ''They're dead! They're dead!'')
But as they narrate, British documentary filmmaker Kevin Macdonald (''One Day in September'') and cinematographer Mike Eley also dramatize the account with real actor-climbers reenacting the Siula Grande event in the Alps. Even in fictionalized form, it's awful to watch a climber fall, or slip into a delirium of dehydration and weakness.... Is that why, perhaps, the filmmakers cushion the pains of ''Touching the Void'' in the kind of whooshing, traffic-directing, mood-coordinating documentary-soundtrack music that can make a viewer want to climb at least a hill to get away from it? The story itself is so powerful and troubling, the moral geometry so vertiginous, and the photography so big that anything other than the natural sounds of snowfall and footfall is a Flat Earth Society intrusion.