THE FLAP CLOSED ACROSS THE ENTRANCE to the sweat lodge, and darkness swallowed Brandon Lay. He could see nothing, so completely did the wool blankets stretched atop the dome's oak-branch frame block the light. He felt the stillness and the rising heat from the fire-baked lava rocks piled in a shallow pit in the center of the room, and heard the sharp inhales and lingering exhales of the nine other veterans squeezed in around him. A Navajo elder named Jonah Yellowman poured water into the pit, and the rocks sizzled. The temperature climbed. Lay sucked in lungfuls of hot air, and the sweat ran faster.

The stifling heat and disorientation of the darkness brought him back to southern Afghanistan, where he had served as a combat engineer, back to the dirt roads and paths that he and his fellow marines had swept for buried bombs. Once, they found 17 on a single stretch. But many bombs found them first. Lay suffered two concussions from blasts on his first deployment, and at least that many on his second. After a friend died and another lost both legs, he wrote to his mom, "I'm just waiting for my time." 

The sweat ritual was meant to welcome them back from war, Yellowman had told them, the way many Native American warriors had been cleansed and brought back into their communities after battle, lest they wander, lost in their memories. This darkness, this heat, was part of the journey. 

The flap opened, and cool air flooded the lodge. Lay squinted at the shock of light, crawled through the opening, and stood under the noon sun. The San Juan River rippled past. A steady breeze rattled the leaves of the cottonwood trees and cooled his sweat-slicked body. He was weak from the heat, but his mind was clear. 

THE VETS SAT AROUND THE CAMPFIRE, their faces flashing pink and orange with the flickering light. It was the night before the sweat ritual and the end of their first full day together on this weeklong trip to Cedar Mesa in southern Utah organized by Sierra Club Military Outdoors. Doug Peacock, Vietnam vet and renowned grizzly bear expert, had come down from Montana to meet them and was telling them his story.

Peacock had served two tours as an army Green Beret medic, which he hadn't expected to live through. He'd carried a map of Wyoming and Montana, and he'd imagine future hiking trips as an escape from the war and the nearness of death. "I used to stare at the map all the time," he said. "In my head, I'd fly like a buzzard over the valleys and basins and explore the country."

After the war, he had made his way to Montana. He'd worked briefly as a fire lookout, and spent many years studying grizzly bears. But first he'd roamed this stretch of Utah, introduced to the slickrock country by Edward Abbey, who would use him for the character of George Hayduke in his novel The Monkey Wrench Gang. 

"This is the place I came to immediately after coming back from Vietnam. I was no good around people. I couldn't even be around my family. I happened to be comfortable in the wilderness because I was brought up that way, so I crawled back into the wilderness." 

He paused. "Eventually, you have to let go and die a little. You have to walk it off." 

As Peacock talked, Lay heard echoes of his own story. He was 29, tall and muscled, with a quick smile and a full beard that would have put him far outside military regulations. He had left the Marine Corps in 2011 and within weeks was enrolled in school and working—to an outsider's eye, a successful transition back to the civilian world. But a sight or sound could still bring him back to Afghanistan, immerse him in memories of friends who'd been killed or maimed and the constant threat of his own death. He sometimes stood in the shower, under the hot water, for a half hour, lost in his private suffering.

He didn't tell others about his struggles or fully acknowledge them to himself; instead, he discovered methamphetamine and quickly found that the drug relieved his misery. He could stay awake for days, then fall into a sleep too deep for nightmares. For a while, he managed to hide his growing addiction from his wife, family, and friends.

In August 2014, after a year and a half of drug use, Lay bottomed out. With his Weimaraner, Wishtan (named after a patrol base in Afghanistan), he left his home in Iowa and drove west. He flung his cell phone into a creek and drove through Wyoming into Montana. He thought about his marriage, his drug addiction, the job he had just lost. He had packed bread, beans, and some cans of soup, but no map. He and Wishtan hiked alone for several days, and for the first time, he felt an unmedicated release from the painful memories of combat. He resolved to end the drug use and find his way home. 

Meanwhile, his wife, Kate, fearful he might be dead, had reported him missing to the police. After Lay phoned her from Montana, she reached out to a veterans group that put Lay in touch with Joshua Brandon, the program coordinator of the Sierra Club's Military Outdoors program, who invited Lay to come with him and some other veterans to Cedar Mesa.

THE GROUP ROSE AT TWILIGHT the next morning, with the stars fading and the eastern sky aglow, to help build the fire that would heat the rocks for the sweat ceremony. Bodhi Tuhawk Whitecloud, Yellowman's friend, called them together outside the lodge, which they and their families had spent the past week building.

Whitecloud had grown up on a reservation in South Dakota; a one-word tattoo across his back announced his tribe: LAKOTA. "This is the sacred way that was passed down," he told the group now. "What I teach you was taught to me by my elders."

Neither Whitecloud nor Yellowman had performed a sweat ceremony for a non-Native American group. But when a friend told Yellowman about the Sierra Club trip being planned for Cedar Mesa, Yellowman, who lived nearby, suggested that the ceremony could help the veterans leave behind their burdens. 

Following Whitecloud's instructions, the veterans placed the first layer of stout sticks east to west and the second, upper layer north to south. They piled cantaloupe-size lava rocks atop the firewood lattice, then stacked kindling and thick wedges of wood around them in a cone shape. Whitecloud lit the fire, and the small flame grew. One at a time, the veterans walked once around the fire, squatted before it, and recited, "To my worst memory," then blew out a sharp breath to stoke the flames. By late morning, the rocks lay in a deep bed of red coals. With a forked pole, a Navajo tribe member plucked out a dozen and piled them in the sweat lodge pit. 

"We come here to suffer," Whitecloud said before the group entered the lodge, "so that we may walk stronger, and so that our walk is good and straight and balanced. Every one of us, we walk wobbly. We don't walk in balance, though we try really hard." 

"If there are things that burden you, that have been hanging over your shoulder, this is a good time to let them go," he continued. "Your work is done. Don't bring it home. It was there. That's where the spirit of it is. Let it lay there. Don't let it walk with you." Barefoot and clad in shorts, they walked single file, clockwise around the fire, then dropped to their hands and knees and crawled inside. 

By the third round, the heat was so intense, a few participants had to leave to keep from passing out. Lay turned his thoughts away from his discomfort and tried to empty his mind. Next to him, Yellowman sprinkled cedar leaves and wood on the rocks, and the lodge filled with fragrant smoke. "When you are sick, you go to a doctor," Yellowman said, his voice low and gravelly, as if rising from the earth. "But the medicine for this illness can't be found in a hospital." He doused the rocks with water, and the steam and heat swelled. He poured on more water and said, "Remember who you are, where you come from, and where you're going." 

They crawled back outside, as slick and wet as newborn babies—children emerging from the earth's womb, Whitecloud had said. They cooled themselves in the shade, then crawled back in for the final round. This time, Whitecloud brought a small rawhide drum into the lodge. "I learned this song when I was a kid, when men were coming home from Vietnam," he said. He beat the drum and sang in Lakota:

A hard path I have walked, none of which I understood.

Because it's my way, I walked forward and prevailed.

Because I listened, now I can put my spear down and wipe the paint.

THE VETERANS LEFT THEIR CAMPSITE along the San Juan River the next morning, their bodies still drained by the ritual the day before. They hiked a mile up a dry creek bed to Monarch Cave, a collection of mud-brick rooms built high off the canyon floor in a deep alcove, protected on three sides by steep canyons, with a commanding view to the east. The inhabitants, likely an extended family of Ancestral Puebloans, had decorated the alcove walls with red handprints. Broken pieces of pottery still littered the ground, along with dried corncobs, remnants of a long-ago meal.

As the others explored the ruins, Lay scrambled down the steep hillside to a wide pool far below the alcove. He stripped to his shorts and dove into the dark water, cold and too deep for him to touch the bottom, then swam back to the edge, pulled himself up onto the grass, and rested. Peacock had told them the wilderness here was special. "It has a human element, a spiritual element. If you're quiet, you can hear the cliffs sing with spirits." Lay closed his eyes and listened. He imagined life here 1,500 years ago—children sent down with clay bowls to fetch water, maybe taking a moment to splash and laugh in the pool. 

Over the next three days, as the group hiked and climbed the canyons, Lay found himself falling into easy conversations with the other vets, trading stories about the military and planning future adventures. The grip of the past was gradually loosening. When bad memories returned unprompted, he focused on Whitecloud's entreaty outside the sweat lodge to let them go, not to let them walk with him. 

The last two days of the trip, the group camped in the bottom of Grand Gulch, on flat rock slabs above the creek bed, where fresh bear tracks zigzagged through the mud. On their last night, Brandon sent them out to explore and reflect.

Lay and two other vets scrambled up the sandstone walls onto rocks high above the camp, their senses coming alive with the sounds and smells of the night. Eyes flashed in the beams of their headlamps—a bobcat still and watching them. Slowly it retreated from the ledge and disappeared. The three worked their way back down toward camp. But instead of returning with the others, Lay scooted under an overhanging piece of the sandstone wall, peered into the dark canyon, and thought about the trip.

He had walked a hard path. He was ready now to walk home.

This article was partly funded by the Sierra Club's Military Outdoors program.