Get ready for a (literally) breathtaking trek up Mt. Everest, from Base Camp at 17,600 feet; through the chilling, corpse-strewn Death Zone; to the very pinnacle of the the Earth, five and a half miles above sea level. For those brave souls who survive the harrowing climb to the top of the world, it is a transformative experience. But can the excruciating ascent—through frigid cold, blasting wind, blinding sun, and severe lack of oxygen—cause permanent, damaging changes to the human brain and body? In the wake of the 1996 disaster that took eight climbers in a single day, scientists follow a team of hikers to measure, for the first time ever, the toll high-altitude climbing takes on the heart, lungs, blood, and brain. Why do seemingly rational people make poor, sometimes fatal decisions as they approach the peak? And the danger doesn’t end there—as NOVA discovers during the descent, when one climber's respiratory illness takes a terrifying turn on the isolated mountainside.