The book begins in the middle of the story, when Krakauer reaches the summit of Everest. Beginning with chapter three, the rest of the chapters are structured in chronological order, following the ascent, summit and descent. Krakauer is at the top of the world, only he is "incapable of feeling much of anything except cold and tired" (4). It has been almost three days since he has slept, and he describes various physical ailments—coughing, separated ribs, trouble breathing and an altered mental s tate due to lack of oxygen. Anatoli Boukreev and Andy Harris, two guides on other expeditions, summit immediately before Krakauer. Krakauer remains on the top of the world for only five minutes, and as he prepares for the descent, he notices some clouds.
The narrative then jumps, moving in time with Krakauer's reflections. He thinks about the questions people would ask him later, after six people had died and other injuries were sustained. People would ask why climbers hadn't turned around upon seeing the clouds Krakauer observed, knowing that bad weather laid ahead. People would ask how mountain guides charging a small fortune for their assistance could push amateur climbers ahead in those conditions. Krakauer offers his own theory, acknowledging that he cannot speak for the guides or for the thoughts of anyone else on the expedition. When he started out that morning, May 10, 1996, he had not seen any indication of the storm that was to follow. He saw the same, seemingly innocuous wispy clouds he'd seen many times before.
The narrative shifts back from thought to action, describing Krakauer's descent. When he begins, he is worried not about the clouds, but about his rapidly dwindling supply of oxygen. He descends quickly, down to the Hillary Step—a stretch of rock famous for its deadliness and difficulty. Upon preparing to rappel down the Step, he sees a crowd of people from three different climbing expeditions waiting to ascend the Step. Krakauer has to wait. Andy Harris catches up to him, and Krakauer asks Harris to turn off the valve on his oxygen tank to conserve the gas. Harris mistakenly turns the valve the wrong way, and ten minutes later, all of Krakauer's oxygen is gone. 250 feet below, at the South Summit, fresh canisters of oxygen are waiting, but until then Krakauer must navigate the descent without supplemental oxygen. As Krakauer waits, members of his team, guided by Rob Hall, and members of an accompanying team guided by Scott Fischer climb past him. Teammate Doug Hansen, climbs by and at the end of the line is Scott Fischer, climbing without any extra oxygen. Fischer, a legendary climber, seems exhausted. Krakauer asks Fischer if he's okay and he says he is. Krakauer finally makes it to the South Summit around three o'clock in the afternoon and hooks up a new canister of oxygen. The weather begins to get treacherous—it begins snowing, and soon it is nearly impossible to see. He reflects on the people now 400 feet above him, celebrating at the summit, unaware of what was to come.