The Sherpas go first, edging up the deadly flank of Mount Everest while international clients wait for days in the base camp below.
They set off in the dark, before the day's warmth causes the ice to shift. They creep one by one across ladders propped over crevasses, burdened with food and supplies, all the while watching the great wall of a hanging glacier, hoping that this season will not be the year it falls.
On Friday, it did.
About 6:30 a.m., as the Sherpas were tethered to ropes, a chunk of ice broke off, sending an avalanche of ice and snow down the mountain's south side, where it engulfed about 30 men. The toll - a dozen dead, four still missing - is the worst in a single day in the history of Everest, climbers and mountaineering experts said.
The disaster has focused attention on the Sherpas, members of an ethnic group known for their skill at high-altitude climbing, who put themselves at great risk for the foreign teams that pay them. Among their most dangerous tasks are fixing ropes, carrying supplies and establishing camps for the clients waiting below, exposing themselves to the mountains first.
A Sherpa typically earns around $125 per climb per legal load, which the government has set at around 20 pounds, though young men will double that to earn more, guides say. Raised on stories of wealth earned on expeditions, they also have very little choice, coming from remote places where there is little opportunity other than high-altitude potato farming.
Friday's avalanche, which killed no foreigners, left many thinking about this calculation.
"All the hard work is done by Sherpas, that is the reality," said Pasang Sherpa, of the Nepal National Mountain Guide Association. "The client will say, 'I did the summit three times, four times.' That is our guest, and we have to accept it. Our job is to make a good scale for the clients, to make this comfortable. We have to do that."
The Sherpas were spread out at an elevation of about 19,000 feet when the avalanche hit, crossing a notorious area known by some locals as the Golden Gate because of the shape of its ice formations, Pasang Sherpa said.
Climbers try to pass it as quickly as possible, but have no choice but to edge across ladders one by one, stretching the crossing to 20 or 30 minutes, he said. Typically, he noted, the teams try to cross before sunrise, when rising temperatures might cause shifts in the ice.
"This morning, our friends started a little late," Pasang Sherpa said. "They arrived at quarter to seven."
Tim Rippel, who is leading a group of mountaineers on the mountain with his company Peak Freaks, wrote that the Sherpas had been moving slowly, hauling "the mountainous loads of equipment, tents, stoves, oxygen and so on up to stock camps."
He was on the phone from base camp just before 7 a.m. local time when an ice chunk started falling, said his wife, Becky Rippel.
The mountaineers were following a popular southern route up Everest from the Nepalese side, but this route means they have to pass underneath the western shoulder and its moving glacier.
Tim Rippel had been watching the glacier, which is a well-known problem, in recent days, but did not think it looked as dangerous as it had in the past, Becky Rippel said.
'EVERYONE IS SHAKEN'
In an update on the company's website a few hours later, Tim Rippel described watching search and rescue efforts.
"I sat and counted 13 helicopter lifts, and 12 were dead bodies flying overhead, suspended by long-line from a helicopter," he wrote. "Everyone is shaken here at base camp. Some climbers are packing up and calling it quits, they want nothing to do with this."
Sherpas are hired to navigate and work above the base camp during the two-month Everest season, said Richard Salisbury, who works on the Himalayan Database, a record of climbs up the mountain.
Apoorva Prasad, founder of The Outdoor Journal, an Indian lifestyle and adventure magazine, described it as "very dirty work," laborious and dangerous.
"These are the guys going up the mountain every season in the least safe way possible," he said.
Foreigners are increasingly bringing their own guides to assist them. In an attempt to secure livelihoods, Nepal this year proposed requiring outsiders to hire a local guide for any ascent above 26,000 feet, which would mean anything near or to the summit.
One such team hit a tense point last April, when three European climbers fought with a group of local guides between two camps. Some Sherpas said the foreign climbers had ascended ahead of their guides while they were fixing lines, violating the custom in Everest climbing.
Nima Nuru Sherpa, the first vice president of Nepal Mountaineering Association, said there's little question that Sherpas take more risks on Everest, mainly because they go ahead to fix lines and set up camp for paying clients.
"Today the incident happened, so we are just feeling sorry about ourselves," he said. "The day-to-day life is very tense. We never know what will happen. So we are not at peace. It's a scary profession, a scary job."