Mountaineer Pemba Gyalje, as seen in The Summit (IFC Films)

In early August 2008, 11 of the 18 mountain climbers who reached the top of K2, the world’s second highest peak, died during the descent, which is regarded as the deadliest 48 hours on the Pakistani peak—second in height to Mount Everest but considered more perilous. What exactly happened is still murky, partly due to the delirium of some the survivors from dehydration, the lack of food and oxygen, the wind and freezing temperature, and also because so many died. It all occurred above 7,900 feet in what’s bluntly called the death zone. According to this detailed and multi-threaded documentary, one out of every four climbers dies on the way down, vulnerable to exhaustion and the fading light.

It was a small world in the Himalayas that summer, with teams from all over Europe, South Korea, and the United States—70 in total—congregating and waiting for the optimal weather conditions to reach the summit before the August humidity increased the risk of avalanches. One could compile a long list of human errors made before and during the trek: not enough rope, a delayed start, slower climbers blocking the trail, unrealistic optimism, limited manpower.

Director Nick Ryan takes a winding but clear route in the retelling, where reenactments flow into the actual video footage from the expeditions that summer. At times the viewer won’t know the difference. But that’s not the film’s main mission. Rather, it settles two scores: what really happened to climber Ger O’Donnell, a mystery uncovered by his family and partner Anne Starkey; and the clearing of Walter Bonatti’s name. Bonatti was a member of the Italian team that was the first to conquer the mountain in 1954, and it took 30 years for him to be recognized as an integral part of the achievement.

Despite the death toll, the tone stays away from the ghoulish—O’Donnell and several other men are seen very much alive not long before the many disasters strike—thanks to the calm, moment by moment interviews, yet the narrative never loses intensity. The film becomes a tribute to bravery, especially that of O’Donnell, the first Irishman to scale K2. Among the executive producers is his friend Pat Falvey, a fellow climber who credits O’Donnell for saving his life during a climb on Mount Everest.

Obvious question: Why would anyone undertake such an endeavor? (Wilco van Rooijen from the Netherlands survived two nights in the open air; he lost all of his toes to frostbite, and continued conquering the Seven Summits, the highest mountain on each continent.) “The bigger the dream, the bigger the risk,” says one interviewee, and the stunning cinematography also partly answers that question: the view at the top is incredible, with K2’s pyramid-shaped shadow looming into China.

The Summit joins a small but distinguished canon, which include Jon Krakauer’s best-selling Into Thin Air and Kevin Macdonald’s gripping documentary Touching the Void.