Nick Ryan has set himself a considerable challenge with this documentary concerning an unprecedented series of disasters that befell mountaineers on K2 in August 2008.

Unlike the makers of Touching the Void, Ryan has a wealth of footage at his disposal. We see climbers huddling in tents. We see breathtaking shots of the world's second highest mountain. But many, many mysteries still surround those events. Ryan and his team – among them acclaimed cinematographer Robbie Ryan – are telling us stories that don't have any certain endings. The result is moving, well crafted and just a little bit frustrating.

Adding skilful recreations to the mix, Ryan does a good job of laying out the known facts. Oddly, the catastrophe was caused by an outbreak of good weather. As many as 10 groups of climbers had been waiting to close on the summit for 60 days. When the skies cleared, fixed lines were applied and the parties began to advance. One error lead to a death. A jam in the notorious Bottleneck resulted and – aggravated by stress and altitude – further crucial mistakes were made. Within two days, as many as 11 climbers perished (some of whose bodies have never been found).

The film is particularly interested in Irish adventurer Ger McDonnell. Revealed as a charismatic individual with an unusually outgoing personality for a climber, the Limerickman looks to have stopped to help trapped colleagues on his descent from the summit. That act of kindness – somewhat against the mountaineers’ unforgiving code of conduct – may have contributed to McDonnell’s death.

Visually impressive and well-researched, The Summit certainly stirs up the terror and mystery that attended that disastrous weekend. But (though unavoidable) the picture's vagueness about certain details leaves us with an irritating number of dangling narrative threads. Moreover, the decision to incorporate the story of an Italian ascent on the mountain from 1954 only serves to slow the film down.

Stirring stuff, nonetheless.