On 1 March 2004 Patrick Berhault and Philippe Magnin set out from Saint Christophe en Oisans for a grand tour of the Alps, the aim being to climb, one after another, all 82 summits of more than 4000 metres, from Oisans to Bernina, taking in Gran Paradiso, Mont Blanc, Valais and the Bernese Oberland. Both climbers are well known for their purist approach to climbing and here again the accent for this large-scale project was on making the most of the pleasures of mountaineering. It was an opportunity to explore the peaks from a different angle, taking new routes and really getting on close terms with them through long exposure. Berhault and Magnin would brave the changing weather, trekking along high-altitude tracks between summits, but the emotional charge would be all the greater. The climbers had the benefit of exceptional know-how, solid experience and proven technique, but this was nevertheless a long journey into the unknown. On 28 April, after almost two months climbing and hiking in the Alps, under conditions ranging from ideal to appalling, they were making their way along Nadelgrat, an interminable ridge leading up to their 67th summit. And there, destiny stepped in… Walking the line at 4000 tells the story of two climbers, scaling peak after peak on a quest that combines idealism and pleasure. But what counts most is their love of the mountains and their friendship.