IT IS IMPOSSIBLE TO AVOID superlatives when talking about New Guinea. Four days into the trek, the team enters a rainforest whose biodiversity is nearly unmatched worldwide. Among its avian species is the bird of paradise—approximately 38 of the world's 40-odd species live here. It is also home to more than 3,000 species of orchids, the world's largest butterfly, its largest moth, the smallest parrot, the largest pigeon, and the world's longest crocodile. The jungles of New Guinea's Papuan Peninsula, in particular, support such an astonishing assortment of trees, ferns, mosses, bromeliads, frogs, butterflies, and rare, night-loving marsupials that the World Wildlife Fund has submitted a proposal to UNESCO to include the entire Owen Stanley Range on its list of World Heritage sites.

Joining our team to guide us over the mountains is Berua, a bone-thin, jungle-wise man whose parents served as carriers for the GIs on the Kapa Kapa. Only seven years old at the time, Berua struggled with them across the spine of the Owen Stanleys en route to the remote community of Jaure. Berua's tattooed 65-year-old wife, Bima, and his hunting dog also join us.

With Berua at the front, we follow the rushing Mimani River into the sodden heart of the rainforest, where sunlight dimmed by a dense mesh of trees, leaves, vines, and fronds has turned the jungle into an immense boiler room. If I was worried about Berua and Bima keeping pace, I shouldn't have been. Papua New Guineans spend their lives walking. For most, it is their only mode of transportation.

We bivouac at the river's edge. Our bush camp consists of a large, blue plastic tarp thrown over a ridgepole, supported by two more poles and tied down to ground pegs. We clear the area of sticks, rocks, and roots and then lay large leaves over the moist ground. I can see George, who is playing the role of expedition skeptic, eyeing the shelter, wondering what is going to keep the snakes out. Twenty-foot pythons and "one-cigarette" snakes like the taipan—whose bite will kill you before you have time to finish a smoke—lurk on the Papuan Peninsula.

Soon darkness presses in, tight and coal black. As if to underscore our vulnerability, the forest becomes an opera house as millions of crickets, cicadas, frogs, "singing" worms, and other strange, boisterous insects and animals wake from their afternoon slumber. As we place our sleeping bags under the tarp, Dave stumbles out of the bushes. He's spent the past 25 years exploring Alaska's remote wilderness areas, but he's never seen a night like this. It is so dark, he says with a laugh, that he couldn't find his pecker to piss with.

Concerned about my knee, I begin walking early the next morning while the team breaks camp. We face a grueling hike to the 9,500-foot summit of what the locals call Mount Ororo. As I climb, a maze of spiderwebs tickles my hands and face. Massive trees, with trunks the size of silos, adorned with lianas and wrapped in a swarm of vines resembling large pythons, reach for the clouds. Less than an hour into the hike, though, I am incapable of admiration. I'm on all fours, pushing through the mud, grabbing at roots, trees, ferns, bushes, leaves, anything I can clasp with outstretched fingers to keep from falling backwards down the steep, slippery mountain. In a cruel twist, everything I reach for is equipped with spurs, thorns, tiny sharp bristles, or swarms of red ants, and my hands sting and bleed.

The porters approach behind me, calling to one another in excited, high-pitched voices, and skip by as if their 40-pound loads weigh nothing. They are off-trail, jumping over downed trees while trying to locate Berua's dog. They do all this without shoes, on broad, thick-skinned feet that make a mockery of my new jungle boots.

Entering the cloudforest, I encounter a scene that inspired the spooked American soldiers to dub Mount Ororo "Ghost Mountain." In the heavy fog, the huge, moss-draped beech trees look like apparitions. Ghost Mountain is soggy, sunless, and silent, suspended in perpetual twilight. The team has caught up with me, and we crest the mountain together. At the top, George quickly notices that the trail catapults down the mountain alongside a steep cliff. "That's comforting," he says. "We might as well throw ourselves off right now."

Cal, one of the young cameramen, apparently takes this as a cue. He grabs a vine as thick as my arm, lets out a deep-woods yodel, and swings out over the cliff and back. He beams. I decide he's been driven mad by the jungle.

To lessen the punishment of the descent, I ride the stream of mud on my backside. Tiny leeches attach themselves to any bare skin they can find and gorge on my blood. Even the porters are tired when we make camp late that afternoon on the slopes of Ghost Mountain, but it's clear they don't want to stop here for the night. It's cold, the wood is wet, fires are hard to start. What's more, they believe that high mountain regions are populated by masalai, or evil spirits. Through the night I wake periodically to find the porters smoking tobacco out of flute-like bamboo pipes, unwilling to sleep.