In 1985, Joe Simpson and Simon Yates, both experienced mountaineers, set out to ascend the previously unclimbed West Face of Siula Grande in Peru. Though they reach the summit, a powerful storm develops and Simpson suffers a badly broken leg in a fall during the descent. The pair attempt a self-rescue, deciding to lower Simpson with ropes down the steep and snowy slope while an enormous storm rages on. Yates cannot see where he is lowering Simpson, and inadvertently lowers him over the edge of a large cliff, leaving him suspended by the rope in mid-air. Yates arrests his fall, but cannot see the predicament his partner is in, nor hear him over the howling wind.