The film portrays the 1996 Mount Everest disaster and the events that preceded it. The film mainly follows Jon Krakauer, the author of the book on which the film is based (Into Thin Air: A Personal Account of the Mt. Everest Disaster (1997)); it also follows the climbing teams of summit guides Rob Hall and Scott Fischer.
The film begins with Krakauer giving a monologue about the events about the disaster. The guides, Rob Hall (Nat Parker), and Scott Fischer (Peter Horton) introduce themselves, their teams, and discuss with the clients how they intend to reach the summit by the set date. Hall's group contains Doug Hansen, a mailman from Seattle, Krakauer, Yasako Namba, and several others. Fischer's group contains a New York socialite, Sandy Pittman, who will perform what Krakauer does for Hall's group, reporting and bring attention. At base camp, Hall speaks with his pregnant wife Jan, in New Zealand, about potential names for their daughter. The groups slowly make their way through camps 2, 3, and 4, and then begin their ascent for the summit. However, in camp 2, Fischer is forced to go all the way back down, so he can take a sick client, Dale Cruz, down for help. Scott refuses help, and returns exhausted and out of breath.
The ascent begins well, with both groups making steady pace. However, upon reaching the bottom of the Hillary step, they realize that there are no fixed ropes. The Sherpa there states it's a two-person job, and the other Sherpa never arrived, mostly due to being too tired and sick from dragging Pittman and all of her heavy equipment all the way up. Mountain Madness guides Anatoli Boukreev and Neil Beidelman set the fixed ropes, but by then dozens of climbers had already reached the step, and now a large jam is at the bottom. Krakauer continues up, and reaches the summit with Anatoli Boukreev, where shortly afterward they are joined by Adventure Consultants guide Andy Harris. Krakauer begins his descent, but reaches the step only the find the jam has only gotten worse, and is forced to wait it out. Meanwhile, Hall is forced to tell client Doug Hansen that they have to turn around and go back. Hansen refuses, as he failed to reach the summit the year before, and he knows he won't be able to afford a third attempt. Hall and Hansen argue before Hall finally caves in and they continue, missing Hall's 2:00 PM turnaround time. Finally, the path down the step clears and Harris begins to descend; Krakauer meanwhile begins to hallucinate from a lack of oxygen. Earlier he had asked Harris to decrease his oxygen flow, but Harris instead increased it, and Krakauer nearly falls over the side, but manages to catch himself. He makes his way down the step and to Harris, and realizes something is wrong with Harris, who thinks the completely full bottles at the oxygen drop are empty. As he descends, he runs into Hansen and Hall, and points out to Hansen that storm clouds are making their way up through the valley and up the mountain.
Shortly after 3 PM, the majority of Hall's and Fischer's groups finally reach the summit. As Krakauer continues his descent, he runs into Scott Fischer, who is completely exhausted and refuses to turn around. Shortly after 4 PM, Rob Hall and Doug Hansen finally reach the summit, where Hall remarks to Hansen that a storm is coming. As he continues to go down, and the weather starts to get bad, Krakauer runs into Beck Weathers, sitting alone by himself in snow. Weathers had eye surgery performed prior to the trip, and has lost vision in his eyes during the summit ascent. He declines to leave with Krakauer, explaining he had promised Rob Hall that he would wait for him to go down. At 4:30, Fischer and his Sherpa, Lopsang, finally reach the summit where Scott feels ill and collapses. Around 5, Krakauer finally reaches the tents at camp 4, where he goes to sleep. The weather continues to worsen, and later, Beidelman, Mike Groom, and the majority of both teams' clients stop to rest, where they run into Beck Weathers, who agrees to descend with them. Storm clouds and thick snowfall cause the guides to lose their positions and not know where they need to go. Higher on the mountain, Hall and Hansen watch as Scott Fischer is dragged by them, so weak he can no longer stand.
Night falls, and Krakauer is awoken in his tent by Rob's Sherpa, Angdorjee, who informs him that the storm is getting increasingly worse, and that Rob and majority of the clients have yet to return. The pair make an attempt to find them, but quickly turn back when they realize the conditions are too treacherous. Meanwhile, Rob attempts to convince Doug to stand up and continue descending, but Doug begs Rob to leave him, telling Rob he will die if he attempts to save him. Rob refuses to leave him behind, and they continue. Scott, suffering from edema, walks off the side of the mountain, and is only saved when his Sherpa pulls him back up with their connected short rope. Scott then begins to fall into unconsciousness, and Lopsang radios for help. Rob continues to struggle down with Doug. In the darkness, Rob slips and falls down, and becomes separated from a hallucinating Doug. He then watches helplessly as Doug, too far away to help, tumbles over the side to his death. Rob is then found by Andy, who attempts to help him up. Andy then leaves, telling Rob he is going to get help. Despite Rob's plea's, Andy continues to go. Andy disappears from view. Rob then hears him cry out, and crawls forward to find Andy's hat lying next to a large drop off, and assumes that Andy has fallen to his death. Rob, buried under snow, communicates with Krakauer attempting to get direction on where he can find oxygen. He gets direction, but then falls down again, and begins to moan. The oxygen bottles are then revealed to be less than twenty feet away from him, but he doesn't see them. Beidelman and Groom's group becomes hopelessly lost, and they take only the clients who can walk with them, dropping Yasuko, Beck, Sandy Pittman, and Charlotte Fox. Scott continues to drift in and out of consciousness, only muttering the words "I am invincible" to his Sherpa, before again losing consciousness. Anatoli Boukreev appears, and helps down Charlotte Fox and Pittman, but is unable to get a third client. Rob begins to hallucinate about seeing his wife Jan, but then snaps outs of it, to realize he is still stuck. He also begins to realize that his hands and his legs are getting extremely frostbitten, and he is having trouble moving. He then blacks out again.
Rob then awakens the next morning, to realize that he is still alive, but barely. He radios the camp, who put him onto the radio with his wife Jan. He asks her if Sarah would be an appropriate name for their daughter, and she agrees. They both tell each other they love them, and then Rob says goodbye to his wife. He dies shortly afterward from hypothermia. Beck Weathers then wakes up, somehow having survived being buried under the snow with no oxygen. Still blinded, he stumbles back to camp, where he receives help. Meanwhile, Anatoli climbs up, and finds the now frozen corpse of Scott Fischer. He says goodbye, and after pulling Fischer's backpack over his face, he leaves. Back at base camp the survivors reminisce about the friends that they have lost.Christopher McDonald as Jon Krakauer
Peter Horton as Scott Fischer
Nathaniel Parker as Rob Hall
Richard Jenkins as Beck Weathers
Tim Dutton as Andy Harris
Jeff Perry as Doug Hansen
Akemi Otani as Yasuko Namba