Tim eventually makes it to Camp 2 at 24,500 feet and decides to go on bottled oxygen a day earlier than everyone else to give himself the best possible chance of summiting. His tactic works and the next day he storms up the mountain, leaving his teammates wondering why they aren't on oxygen, too.

Mogens is left agonizing over the same decision. He's made it to Camp 2 but he suffered a bad asthma attack during the climb and his confidence is at rock bottom. Russell tries yet again to persuade him to use oxygen, but Mogens needs time to think. He's failed three times already. "It's my job to let people like Mogens go as far as they can without actually killing themselves," says Russell, "but it makes me pretty nervous."

Team 1 fights their way to Camp 4 at 27,500 feet inside the Death Zone, where their bodies are slowly dying from lack of oxygen. It's a grim place at the best of times, but as they arrive, they're met with the sight of a dead climber lying in the snow. "Oh dear, there's a body there," agonizes Rod. "I've just seen a body — I want to go, it's bad karma. If he can die, we can die."

They'll leave Camp 4 at midnight to begin an 18-hour Summit Day. But as they prepare for the toughest day of their lives, another team is in dire straits. A team of climbers has become separated from each other high on the mountain. It's chaos — their teammates don't know where they are, but they want Russell to help. Russell pulls a Sherpa off the summit team to search for the missing climbers. Eventually one is found, but the other remains missing and is presumed dead.