Joe Simpson and Simon Yates narrate the recounting of their feat as director Kevin Macdonald interweaves enacted scenes with Brendan Mackey as Simpson and Nicholas Aaron as Yates. The film is based on Simpson's book. A striking realism is achieved on the locations used, some on the Peruvian mountain, others in the Alps, giving the viewer a feeling of being on the spot.

The moral issue rises from a jolting decision that Yates made. The men were doing well in their climb when Simpson suffered a badly shattered leg in a fall. Aborting the climb at that point, the pair began come down with Simpson being lowered on a rope. But accidentally Simpson was lowered over an edge that dropped him dangerously far and out of sight. He could no longer be detected pulling on the rope. It looked as if Yates, his strength waning, would be pulled down to his death with his partner and he made the decision to cut the rope to at least save his own life. Simpson subsequently said Yates made the right decision, one he would have done if their places had been reversed.

The film then deals with Simpson's excruciating ordeal. Determined to survive, he uses his resources to inch his way down in constant danger of plunging to his death, all the while in terrible pain and fighting the elements. It is thrilling to watch the re-staged, heroic struggle until, against all odds, Simpson manages to get to safety and desperately needed help.