Guides Rob Hall and Scott Fischer lead two groups who plan to reach Mount Everest's summit. The groups make their way through Camps 2, 3, and 4, and begin their ascent to the summit. In Camp 2, Fischer is forced to climb down with a sick client, Dale Cruz, for help. Fischer refuses help and returns tired.
Both groups reach the bottom of the Hillary step, and discover there are no fixed ropes. The Sherpa there states it is a two-person job and the other Sherpa never arrived, due to being tired and ill from dragging climber Sandy Pittman (from Fischer's group) and her equipment up. Mountain Madness guides climbers Anatoli Boukreev and Neil Beidelman, who set the fixed ropes. By then dozens of climbers have reached the step, and congestion forms at the bottom. Climber Jon Krakauer (from Hall's group) continues to the summit with Boukreev. They are joined afterward by Adventure Consultants guide Andy Harris. Krakauer begins to descend and finds the jam at the step has worsened. He is forced to wait.
Meanwhile, Hall tells climber Doug Hansen they have to turn back. Hansen refuses, as he failed to reach the summit the previous year and cannot afford a third attempt. The two continue, missing Hall's 2 p.m. turnaround time. When the step clears, Harris begins to descend. Krakauer begins to hallucinate from lack of oxygen, as Harris increased his oxygen flow when Krakauer asked for it to be decreased earlier during the climb. After making his way down to Harris, Krakauer realizes something is wrong with Harris, who thinks the full bottles at the oxygen drop are empty. After 3 p.m., most of the members of both groups reach the summit.
Krakauer continues his descent and runs into Fischer, who is exhausted and refuses to turn around. After 4 p.m., Hall and Hansen reach the summit. As the weather worsens, Krakauer finds Beck Weathers sitting alone in the snow. Weathers had eye surgery prior to the trip and lost his vision during the ascent. He declines leaving with Krakauer, having promised Hall he would wait for the latter. At 4:30 p.m., after reaching the summit with Sherpa Lopsang, Fischer collapses. Krakauer reaches Camp 4 and goes to sleep. Beidelman, Mike Groom, and most of the clients stop to rest. They encounter Weathers, who agrees to descend with them. Storm clouds and snowfall cause the guides to become lost. Higher on the mountain, Hall and Hansen drag Fischer, who is too weak to stand.
Night falls, and Krakauer is awoken by Sherpa Angdorjee, who says Hall and most of the clients have not returned. The pair searches for them, but eventually finds conditions too treacherous. Hall and Hansen continue descending. Fischer, suffering from edema, walks off the side of the mountain. Lopsang saves him by pulling him back up with the rope connecting them. Fischer begins to fall unconscious, and Lopsang radios for help.
Hall, struggling with the hallucinating Hansen, slips and falls. The two are separated, and Hall watches Hansen fall to his death. Harris finds Hall and tries to help him up before leaving to get help, despite Hall's pleas. Harris disappears from Hall's sight but cries out. Hall crawls over to find Harris's hat lying next to a drop and assumes the latter fell to his death. Buried under snow, Hall gets directions from Krakauer to an oxygen supply, but falls down. He does not see the oxygen bottles nearby.
Beidelman and Groom's group becomes lost. The guides take only the clients who can keep up with them, leaving behind Namba, Weathers, Pittman, and Charlotte Fox. Boukreev helps Fox and Pittman descend but cannot get a third client. Hall hallucinates about seeing his pregnant wife Jan (who is actually in New Zealand), then snaps outs of it. His hands and legs are frostbitten, and he has trouble moving. He blacks out again.
Awakening the next morning, Hall radios the camp and speaks with Jan. The couple decides to name their daughter Sarah. Hall says goodbye to his wife and dies from hypothermia. Weathers awakes, having survived being buried under snow without oxygen. Still blinded, he returns to camp and receives help. Boukreev climbs up and finds Fischer's frozen body. After covering Fischer's face, he leaves. Back at base camp, the survivors reminisce about the friends they lost.
