Mogens Jensen, an asthmatic, attempted to summit Everest without supplemental oxygen.

Above 26,000 feet (8,000 meters) it's called the Death Zone. The body can't use food, so it burns its own muscle tissue instead. All but the truly hard or insane are constantly on bottled oxygen because there's just one-third of the oxygen here that we breathe at sea level. Imagine opening a window while flying on a 747. That's what it's like in the Death Zone.

Mogens is one of those who is truly hard or insane or a bit of both. He wants to climb to the summit without oxygen and he's an asthmatic. He's fitter than anyone else on the mountain and everyone expects him to succeed without problems.

I follow him out of Camp 3 fully expecting not to be able to keep up with him, but 45 minutes in, I'm still with him. I roll tape and he says he's taking it easy and saving his energy for the final day, but soon he's on the floor, calling Russell on the radio.

I climb back down to him and he tells me he's in trouble. He's sick, dizzy and afraid. Afraid isn't something I expected. I guess I just thought people get to the top or give up, but 26,000 feet up on a 10,000-foot cliff, days from any help even if you're so dizzy you can't walk a straight line anymore — I guess afraid is right.

Together we climb back down to Camp 3 and I give Mogens my oxygen. It doesn't help and he's throwing up in the snow. Suddenly it's all over for him and he cries.

Camp 4

Mogens heads down the mountain with the Sherpas, but I have to get to Camp 4 and the day is fast running out. It's the hardest climb yet, and endless. I arrive just before dark and collapse into the tent with Ken. Our tent is perched on the edge of a huge drop, almost 10,000 feet down to the Rongbuk Glacier. One corner of the tent is actually over the edge of the drop-off.

It's an uncomfortable night — crammed into the tent with us is a huge pile of camera gear, so there's barely room to lie straight. Most of our time is taken up melting snow for water. We must drink as much as possible — Ken needs enough to see him to the summit and back.

We sleep on oxygen, but every 20 minutes or so the condensation building up in the mask overflows and dribbles cold spit back into my mouth. It's a disgusting addition to our grim situation.

It's midnight and we're up again. The team is leaving at 1 a.m. for the summit. It's bitterly cold, maybe minus 30 degrees C. Everything in the tent is covered in a layer of ice, including the camera equipment. Outside I switch the camera to infrared and catch a quick comment from Bill and Terry before they head off into the darkness.

Ken's gone. Now I'm completely alone and it feels so cold that if I didn't blink, my eyeballs would freeze. I climb back into the tent for the long wait. It'll be at least 16 hours until I see them again. I'm wearing several layers of underclothes, a down suit, balaclava and woolly hat, and I'm zipped up inside a sleeping bag and I'm cold.

I fall asleep for a few more hours and wake up confused about where I am and what I'm doing here until I realize that my oxygen has run out. I crawl outside and grab another tank, hook it up and get back to work melting snow to drink. It's not until Russ checks in that I'm truly grounded again and I chip the ice from my camera before climbing out into the sunlight and start filming.

In the thin atmosphere at this altitude the sky is dark blue overhead. The surrounding mountains of the Himalayas poke up through the cloud layer miles below me. Above, the route to the summit climbs steeply to the northeast ridge of Everest, and over the nearest horizon I can see the Second Step. At midafternoon, Terry, Bill and Ken are stuck on top of the step behind 20 other climbers. I grab a tripod and try to get long lens shots. Team 2 begins to arrive on their way up. Every one of them is shattered and gasping for air. When Jen and Mark, my relief team, get into Camp 4, I can think about leaving. I wait for Terry and Bill to get down from their summit attempt and then I’m outta there.