Night closed over Laos, where clouds were piling up over the rugged mountain jungle. An American pilot, on a mission to disrupt enemy traffic bound for North Vietnam, was flying into trouble. The artificial horizon on his A-1 Skyraider, a single-prop workhorse of World War II vintage, had suddenly stopped functioning, making it impossible for him to gauge his position among the clouds.

Dizzy and disoriented, Air Force Capt. Michael J. "Bat" Masterson radioed to a companion flying nearby that he was ejecting.

"I'm losing it and getting out," Masterson barked.

At this, the wingman, Air Force Maj. Peter W. Brown, began a sharp turn to avoid colliding with Masterson. Halfway through this maneuver, Brown saw an orange fireball light up the jungle. Masterson's plane was down. Brown noted the time and date—6:55 p.m., October 13, 1968. But where was Masterson?

Brown circled the crash site for more than two hours, searching for some sign of life, until his fuel gauge dipped dangerously low, forcing him to break off and return to home base in Thailand. Other aircraft took over the search at first light, scanning the site for hints of movement. There were none, just the fuselage of a Skyraider drilled into the steep mountainside, a pair of broken wings smoldering nearby, but no Bat Masterson. Had he parachuted to safety? Had he been captured by Pathet Lao troops, the Communists controlling this corner of Laos? Had he ridden his Skyraider into the ground?

Those questions would remain unanswered for almost 40 years—through clandestine night raids on Laos, through days of fighting along the border with Vietnam, through the sanguinary years that finally ended the war in April 1975. A long, hard silence followed, with little contact between the United States and its former enemies who controlled the battlefields of Vietnam, Laos and Cambodia. The victors, more interested in rebuilding their lives than in helping Americans find lost compatriots, kept the doors closed until the scars of war began to heal. The impasse plunged more than 1,800 Americans listed as missing in Southeast Asia into a kind of limbo, like the wandering phi pheth ghosts of Lao tradition. Masterson—nicknamed for the frontier gambler and deputy marshal who shared his surname—became one of these missing souls, lost between the world of the living and the dead.

Meanwhile, back at home, Masterson's family held out the hope that he was still alive. Two daughters, ages 11 and 6 when their father disappeared, eventually acquired MIA bracelets engraved with his name, which they pledged to wear until his return. Masterson's wife, Fran, recalled one of her last conversations with Bat, who told her how he dreaded night missions over Laos.

After Fran got word of Masterson's crash, she flew to Southeast Asia to search for her husband while the war was still raging. After a few weeks, she returned to Upland, California, and continued to wait. She played and replayed the taped messages Bat had mailed home before his crash.

Years passed. She put the tapes away. Masterson was promoted, in absentia, to lieutenant colonel. Hope flared when his name appeared, along with 20 others, on a list of prisoners captured in Laos and transferred to Vietnam. But the others on that list, from a 1972 report by the Defense Intelligence Agency, came home alive; Masterson, who had been included erroneously, remained at large. A decade after the 1968 crash, his status was routinely changed to missing in action, presumed dead. While many grass-roots activists believe that former enemies may still hold Americans captive, a lengthy investigation by Senators John Kerry, John McCain and others found no evidence of any POWs remaining in the region. Their 1993 report was unanimously approved by a Senate select committee.

Fran Masterson never remarried. She still dreamed about her husband, who was a boyish 31-year-old at the time of his disappearance. In those dreams he remained young, wandering the jungles just beyond reach. "Most of the time he doesn't know who I am," Fran Masterson told an interviewer in 2004. "Maybe it's the not knowing of what happened to him that makes it so hard." Frustrated by a lack of progress, she became a founding member of the National League of Families, an activist group that lobbies on behalf of missing service members, who are more numerous than one might imagine.

The United States counts more than 88,000 Americans as missing from its recent wars—some 78,000 from World War II; 8,100 from the Korean War; 1,805 from the Vietnam War; 126 from the cold war; one from the Gulf War of 1991; and one from the current Iraq war. About half are considered "unrecoverable," lost at sea or sequestered in sunken vessels.

But another 45,000 are thought to be recoverable, and in the years since Vietnam, military investigators, working with civilian scientists from the world's largest forensic anthropology laboratory at Hickam Air Force Base next to Honolulu, have made an arduous effort to whittle down the roster of the missing. Although focused initially on Southeast Asia, the recovery missions have circled the globe, from Tibet to Hungary to Russia and Papua New Guinea. More than 1,200 service members have been recovered and identified since 1973. Most of these—841 by the military's tally—were repatriated from battlefields in Southeast Asia; others came from North Korea, China and the scattered theaters of World War II.

A number of factors have contributed to the recent surge in recovery and identification operations. Prodding from people like Fran Masterson and other family members has created a strong political constituency for POW and MIA work, boosting the federal budget and personnel for the Joint POW/MIA Accounting Command (JPAC), the military unit charged with finding missing warriors. At the same time, advances in forensic science and DNA testing make it easier to identify a long-dead soldier or sailor on the basis of very little physical data—a bone fragment, a few teeth, a lock of hair—even in cases which have languished unsolved for decades. And, since the mid-1980s, improved relations with Vietnam and other Asian nations has meant better access for teams scouring the jungles for evidence. All of this has led to the growth, in sophistication as well as size, of the JPAC command, which employs more than 400 people and combines expertise in criminal investigation, archaeology, linguistics, bomb disposal, DNA processing and a number of other specialties for a single purpose—to account for all Americans who ever disappeared in battle.

"Nobody goes to the effort we Americans do," says Army Brig. Gen. Michael C. Flowers, commander of JPAC, headquartered at Hickam Air Force Base. "From the time we go to boot camp we learn to take care of one another. And we make the promise that no one gets left behind. We will go back again and again to look for those who might still be alive or those who have fallen."

It took some persistence to find Bat Masterson's crash site. By the autumn of 2005, when I arrived in rural Xieng Khuang Province of Laos with an anthropologist and a recovery team of nine service members from JPAC, the United States had already spent years in delicate negotiations for access to the region. Since the war, there has been periodic unrest among the indigenous Hmong hill tribes, old allies of the French and, later, of the Americans who fought there. Central authorities in Laos, a Communist regime since 1975, were understandably touchy about opening the region. Thus it was 1993 before the first investigators were admitted to northern Laos to search for Masterson, with follow-up missions in August 2004, October 2004 and July 2005.

Each foray into the mountains yielded a few scraps of new evidence—a 1967 quarter from the site, which fit the time frame of Masterson's disappearance; two 20-millimeter cannons consistent with the A-1 Skyraider's armament; parts from the plane's parachute assembly; many fragments of the blue glass used exclusively in the Skyraider's canopy; and a few shards of bone thought to be human. The bone was in such small pieces and so badly burned, however, that it contained little organic material, which made it an unlikely source of DNA to link Masterson and the wreck.

But the crash site—prosaically logged in military records as Case No. 1303—was almost certainly Masterson's: it fit the coordinates noted by his comrades in 1968, and the aircraft debris made it clear that the downed plane was a Skyraider, the only one of its kind lost in this part of Laos. Although the place had been thoroughly scavenged prior to our arrival by villagers looking for scrap metal and other useful bits of hardware, members of the recovery team were optimistic that a month's excavation might finally solve the mystery of Masterson's fate.

"We're just now getting into a very productive part of the dig," said Elizabeth "Zib" Martinson Goodman, the civilian anthropologist in charge of recovery operations. Goodman, an ebullient 36-year-old raised on an apple orchard in central Washington State, showed me around the site, where a swath of jungle had been peeled back, revealing a grid of four meter squares climbing down the mountainside and ending where a dense green wave of vegetation reared up at the edge.

Near the top of the cleared area was the impact crater, a black hole in the red earth. "On most archaeology sites," said Goodman, "you dig down through the topsoil, sifting for artifacts until you reach the sterile layer, the undisturbed layer of soil below the surface." On this hillside, the stratigraphy was confused. The plane punched through the sterile profile. Scavengers later excavated around the plane, tossing the dirt containing wreckage and human remains down the hill. Monsoons subsequently scattered the evidence. Any remaining artifacts would be dispersed downhill from the crater.

That is where a marine and a soldier, stripped to their T-shirts and sweating, chopped away with pickaxes at the lower edge of the clearing. Each shovel of dirt was dumped into a black plastic bucket labeled for this particular grid and conveyed up the hillside by a brigade of some 50 Hmong workers. On the brow of the hill, a score of Hmong villagers, working with Americans from the JPAC team, strained each bucket of soil through quarter-inch screens to recover the tiniest clues from the site—twisted bits of olive drab metal, mud-streaked screws and rivets, strands of insulated wire, melted gobs of plastic and the occasional stinging centipede lurking in the dirt. One afternoon, as I was sifting earth at the screening station, I uncovered a scorpion in my tray. A Buddhist co-worker walked over, calmly lifted the irate arachnid out with a trowel, set it free at the jungle's edge and blithely returned to work.

The excavation looked like textbook archaeology, laid out with pegs and strings in geometrical precision, but in other ways it was unique. "Most archaeology gets done in places where people want to live," said Goodman, "like flat places where you can walk around." As she spoke, we were listing like sailors on a heeling sailboat, straining to keep balanced on the nearly 45-degree slope. "We often wind up in places like this, where it's pretty remote and hard to maneuver, or in Papua New Guinea, where we work knee-deep in cold water and mud the whole time," she said. "Half the challenge is just getting there and being able to work." In July 2005, the previous season at Site 1303, frequent rains shut down excavations for days, and on those occasions when work was possible, the footing was treacherous. "The challenge was to get up the hill without breaking your leg," said Goodman, who had supervised the previous excavation.

Our conversation was interrupted by the crackling of a two-way radio on Goodman's hip. A disembodied voice came from the speaker: "We've got something for you."

Another radio voice answered: "Roger. I'm on it." The second voice belonged to Staff Sgt. Steve Mannon, 32, a burly marine in wraparound shades and a dark green polo shirt, who was already scrambling downhill, where workers with picks and shovels had backed away from the hole. They made room for Mannon, the team's unexploded ordnance (UXO) expert, who got calls like this throughout the day. He had come to examine a rusty-looking cylinder, about the size of an egg roll, which the diggers had turned up. Mannon pulled off his sunglasses, squatted in the pit and opened a knife, using the blade to pick the mystery object out of the dirt. "Another 20-millimeter round," he pronounced, easing the ordnance into a satchel, clapping his shades back on and trudging uphill to a jungle path at some distance from the work area. We stopped under a red and white sign emblazoned with skull and crossbones and a warning in English and Lao: "DANGER!!" it read, "UXO!" Just beneath it was a pit in which Mannon had collected another 50 such rounds, part of the Skyraider's 2,000-pound payload. He added the morning's find to the growing pile, which would double in size in the course of our weeks here.

"What would happen if you set off one of these rounds?" I asked him.

"Depends on where you hit it," he answered. "You could be blinded, or it could just take most of the meat off your hand."

When this dig was finished, Mannon would bury the recovered explosives to forestall an accidental detonation—a constant threat to farmers or anyone else who puts a spade to earth in this ordnance-packed landscape.

The United States dropped more than two million tons of explosives on Laos between 1964 and 1973, making it the world's most heavily bombed nation per capita, according to the United Nations Development Program. In the years since, the United States has spent millions to disarm ordnance in Laos, but bombs remain a hazard. That is why each recovery group is assigned a specialist such as Mannon, one of several team members on loan to JPAC for this mission.

Like other people deployed here, Mannon had seen combat in the current Iraq war. He admitted that he missed the excitement of battle, but he found the work in Laos rewarding. "There is no more honorable mission than this one—bringing one of our guys home," he said.

Even across the distance of time, a special bond links Bat Masterson to comrades who never knew him. "It's part of the code, man," said Sgt. Daniel Padilla, a soft-spoken 22-year-old marine from San Antonio, on loan to JPAC as radio man and communications specialist. He held out his right arm to illustrate the point. There, between his elbow and wrist, the code was tattooed in blue ink:

We few, we mighty few, we band of brothers, for he today who sheds his blood with me, shall forever be my brother.

"It's from Shakespeare," Padilla added. "This is when King Henry V is about to go into battle and he's rallying the guys." The tattoo artist had edited Shakespeare slightly, substituting "mighty" for "happy" and inserting "forever" in the last line, but the sentiment remained true to the original.

In most criminal investigations, a case is considered “cold” if it remains unsolved for more than two weeks. The investigative trail in most of the JPAC cases, by contrast, has been cold for 20, 30 or 40 years, with witnesses dying, landscapes shifting and evidence degraded by time and weather, as at Site 1303. “It’s a puzzle with 10,000 pieces scattered around us,” said Mannon, gazing down at workers screening soil and hoisting buckets of dirt up the mountainside. “We’ve got to figure out how all the pieces fit together.”

After a few days of digging, those pieces began to pile up, making it look as if Bat Masterson had not bailed out after all, but had perished on the hillside in 1968.

By early November, Goodman had examined and bagged several hundred pieces of bone, which she labeled as “possible osseous remains,” for future scrutiny by JPAC’s Central Identification Laboratory in Hawaii. Like the bones recovered previously from the site, these were burned bluish gray and broken into fragments the size of a fingernail, too damaged and small for DNA sampling, which usually requires at least two grams of dense bone, such as from an arm or a leg. Three other bone fragments from the site were also too damaged for DNA, but they were nonetheless big enough for Goodman to see that they were human. Since there was no village at Site 1303, no cemetery there and no history of human occupation, it was reasonable to suppose that the remains belonged to Bat Masterson.

Other evidence pointed toward that same conclusion. Three more coins—nickels dating from 1963, 1964 and 1965—were recovered, as were more than 30 unfired rounds from a .38-caliber weapon, most likely the sidearm Masterson carried on flying missions. "Most pilots carried a sidearm like that," Goodman said. "If you ejected from the plane, you'd keep it with you in the jungle. It wouldn't be with the wreck unless you were with the wreck."

While Goodman talked, cicadas buzzed high in the trees around us and a boombox near the impact crater churned out an odd mix of Elvis, Lao pop, zydeco tunes and a piece that I was old enough to identify as Wild Cherry's only hit "...Play that funky music, white boy! Play that funky music right!" This tune caused Hmong and Americans to dance as they sifted dirt, picked out artifacts and passed them along to Beth Claypool's roost on the hill above the screening station.

Claypool, 21, a Navy Parachute Rigger Second Class and the mission's "life support analyst," spent afternoons sorting through hundreds of pieces of broken metal, wiring, tattered cloth and other gleanings to determine their hidden importance. She traveled with a library of technical manuals and old photographs, which helped to identify occult bits of aircraft engines, rivets, snaps and buckles emerging from the dirt. I often sat with her at the sorting station and marveled at her ability to separate gold from dross. One day she pulled out a slab of rust, studied it for a few seconds and declared it a pocket-knife. "See the metal loop on the end of it?" she asked, pointing out the clasp that might have secured a line to the owner's vest. Setting aside the knife for Goodman to examine, Claypool turned her attention to an ordinary-looking screw with an oversize head and a short body. Noticing that it was threaded unconventionally—it tightened to the left instead of the right—she determined that it was the visor adjustment device from the top of a pilot's helmet; thus, its reversed threading. "No other screw looks like that one," she said. The rest of the helmet was never recovered, but this small piece of metal would prove to be a critical bit of evidence placing Masterson with the wreck.

Investigators have learned that even seemingly insignificant items can hold special meaning, especially for family members who often recognize the quirks of loved ones among personal effects. "We don't ignore any of that evidence," said Army Maj. Rumi Nielsen-Green, a media officer for JPAC. "We've had cases in which a wife knew that her husband always carried a combination of lucky coins, or a sister remembered the bundle of rubber bands her brother kept in his pocket. You never know what is going to help close the circle."

In the days ahead, other artifacts would emerge to round out the picture—the fragmentary remains of a parachute still folded neatly into a corner of its pack, a harness buckle, several zippers from a flight suit, a captain's rusty insignia pin and a metal insole from a pilot's boot. The insole was surprisingly small—size seven or so—but it was a likely match for Bat Masterson, who stood 5 feet 5 inches tall and weighed 137 pounds. "I knew what it was as soon as I saw it," said Navy Cdr. Joanne Petrelli, who uncovered the insole while swinging a pickax in the pit one afternoon. "It was the shape of a human foot. It was about the size of my husband's foot. He's small, too—and he's a marine."

While strongly suggestive, such evidence was hardly conclusive. That changed on the day that Army Sgt. Christophe Paul, 33, a combat photographer attached to JPAC, discovered a clay-caked sliver of metal in his screening tray, rubbed off the mud and reached for his radio.

"Hey, Zib," he said. "What is the name of the guy you are looking for?"

"Michael John Masterson," she answered.

"I think I have his ID tag here."

Goodman came bounding over, examined the dog tag and rendered a verdict: "Looks like Chris is buying the beers tonight," she said, setting off a ripple of cheers down the hillside. Everyone crowded around for a look at the tag, which was stamped with Masterson's particulars. Goodman also noticed that the tag was bent, as the insole had been, most likely from the impact of his crash.

For Christophe Paul, a French native who joined the Army in 1999 and became a U.S. citizen in 2005, this moment of discovery fulfilled a dream. "I have been fascinated by archaeology since I was a little boy when my mother took me to see a King Tut exhibit in Paris. Now here I am doing it! I was so happy to find this ID, so we can get this guy home again."

Like Paul and other members of the armed forces, Masterson had worn two dog tags. Air Force Tech. Sgt. Tommy Phisayavong discovered the second one, bent like the first, in the screening station a few days later. Like Paul, Phisayavong had immigrated to the United States and become a citizen, but his journey had been torturous by comparison. Born and raised in Vientiane, the capital of Laos, he fled the country in 1978 after three years of the Pathet Lao regime. He was 13 at the time. He crossed the Mekong River to Thailand under cover of darkness, accompanied by his 10-year-old brother. They joined an uncle in a refugee camp there, and one by one, other members of the family crossed the river. Eventually, they made their way to the United States, where they settled in California.

"I never thought I'd see Laos again," said Phisayavong, who joined the Air Force in 1985 and was eventually assigned to JPAC as a language specialist. Now a veteran of many recovery missions, he sees Laos all the time, acting as interpreter and cultural envoy among team members, Lao officials and Hmong villagers like the ones who trudged several kilometers to work at our site each day.

Sifting dirt with the Hmong, I often wondered what they thought of our sudden appearance among them, this ragtag crew of Americans in sunglasses and muddy jeans, arriving in a swirl of dust whipped up by helicopters. I wondered what they thought of our raucous music and our tepid enthusiasm for the steamed bee larvae they thoughtfully provided as a morning snack. Most of all, I wondered how the Hmong regarded our compulsion to comb through the earth for the scanty remains of a man who had been resting here for so long, seemingly forgotten.

I was never able to speak to the Hmong about these things because Lao officials, still nervous about foreign contact with the tribesmen, discouraged conversation. But Tommy Phisayavong provided some insight, based on his own long experience in the territory. "It may seem a little strange to them that we go to these lengths to find people," he admitted. "You know, most of them believe that when you die, you stay where you are and that's that. We try to explain why it's important for us to bring the dead back and put them to rest. We've done enough of these missions over the years that I think maybe they understand that it's part of our ritual."

Our own rituals of digging, screening and sorting began to pall after almost a month, the buckets yielding progressively less as the excavation approached the edge of the jungle. "That's just what you want," said Goodman. "You don't find much at the beginning. You find a lot in the middle. And it tapers off at the end. That means we've been digging in the right place."

Despite the chaos of the wreckage, the extensive scavenging and the acidic soil eating away at bone and steel for nearly four decades, the team had culled more than enough evidence to close Site 1303. When we decamped from Laos, the jungle would creep in and gradually obscure the drama of loss and restoration that had unfolded here.

What little remained of Bat Masterson was carefully labeled and placed in 26 small plastic bags, each keyed to the place and date of its discovery. Other artifacts, consisting of personal effects and material evidence, filled another 75 bags. The entire yield fit neatly into a black Pelican briefcase, which Goodman secured with two brass padlocks and kept in her possession for the long journey home. To guarantee the integrity of these investigations, JPAC follows a strict protocol, maintaining a chain of custody from field to laboratory, as if the evidence had to withstand courtroom scrutiny.

Goodman's Pelican case stayed within reach on a crowded military flight from Pattaya, Thailand, where we joined other teams returning from operations in Laos, Vietnam, Cambodia and Thailand. It had been a good season for some, indifferent for others. Three or four MIA investigations would be resolved as a result of their work, and there would also be new missions: members of one investigative team told me that they had pinpointed ten new sites for excavation in Laos alone. Other projects in the region, and from World War II, would keep JPAC busy for years to come.

Critics might wonder if the elaborate effort is worth it. At a time when the United States is engaged in war on two fronts and the military is sorely pressed for resources, was this exercise an extravagance?

Goodman had heard this question before. "We owe it to the people who made the ultimate sacrifice," she said. "There were bad feelings about what happened in Vietnam. The people who went there never got the recognition they deserved. We owe it to them and to their families to make this extra effort now, as a kind of reparation."

After a 20-hour flight through darkness, nearly 200 bleary-eyed soldiers, marines, sailors, airmen and civilians staggered off the plane into the blinding afternoon sun at Hawaii’s Hickam Air Force Base. There were no brass bands and no honor guards to mark this homecoming. Those ceremonies would come later, after the findings from our recovery team—and those from others—had been subjected to rigorous scientific review in the Central Identification Laboratory. Only then could identifications be confirmed, families briefed and remains sent home for burial.

In the meantime, Goodman and the other anthropologists signed over their evidence to the laboratory, which triggered the meticulous review process. While she wrote her excavation report, the rest of the case was analyzed by other lab specialists and finally sent for outside review.

"There's peer review at every step," explained Thomas Holland, the lab's scientific chief, who collects the outside reviews and scrutinizes them. "That's when I write the final report, which makes the identification and spells out the justification for it. By that time the case has to be airtight."

Depending on the quality of the evidence and the complexity of the case, a review can take up to a year. This can be excruciating for families who have already endured so much—but it would be even worse if the process concluded with a case of mistaken identity. "We don't want any doubts," said Holland. "Our goal is to make certain that there is never another unknown soldier."

It seems unlikely that there ever will be, given the forensic techniques available today. Last year alone, the Central Identification Laboratory resolved a hundred cases, almost evenly divided between Vietnam and World War II. Some were identified by DNA sampling but most by dental records, still the most reliable means of providing a name for the dead.

Since neither teeth nor DNA was available in Masterson's case, it was finally closed, February 7, 2006‚ on the basis of circumstantial evidence. Later that month, Air Force officers presented the findings, along with Masterson's dog tags, a few coins, other effects and a copy of the case file, to his wife.

Her reaction was surprising. "I told them I didn't agree with any of it," she said. "It's all based on circumstantial evidence. I still don't know that he is dead or alive. He could be in a POW camp." Fran clings to that hope, based on the 1972 intelligence report that listed Masterson as captured.

But what about the dog tags, the bone fragments, the unused parachute, the insole matching her husband's foot size?

"All circumstantial," she said. "They just want to close this case and get it off the books. We've gone all this time. What's the hurry?"

She has appealed the findings, which will be reviewed by a board of senior military officers from all service branches, and if necessary, returned to the laboratory for further investigation.

Meanwhile, the remains of Bat Masterson will stay where they have been since last Thanksgiving, locked in a Hawaiian laboratory, halfway between Laos and home.

Robert M. Poole was executive editor of National Geographic. Photographer Paul Hu lives in Hong Kong. Army photographer Christophe Paul is based in Washington, D.C.