For Matthew Alan Sheppard, all of the anxiety, deception, and delusion converged in one moment on a crisp winter weekend in February 2008. From the outside, he hardly seemed like a man prepared to abandon everything. At 42, he'd been happily married for 10 years, with a 7-year-old daughter and a comfortable home in Searcy, Arkansas. An environmental health and safety manager for the electrical parts maker Eaton, he'd risen in three years from overseeing a plant in Searcy to covering more than 30 facilities throughout North and South America. A recent raise had pushed his salary close to six figures. To his coworkers and hunting buddies, he seemed an amiable guy with a flourishing career.

To Sheppard, though, that same life felt like it was collapsing in on itself. With his promotion had come the stress of new responsibilities and frequent travel. He had been steadily putting on weight and now tipped the scale at more than 300 pounds. Financially he was beyond overextended. A gadget lover whose spending always seemed to exceed his income, he had begun shifting his personal expenses to his corporate credit card — first dinner and drinks, then a washer and dryer, then family vacations. In early February, when an Eaton official emailed to inquire about his expense reports, he felt everything closing in. He began devising a plan to escape.

So on a Friday two weeks later, Sheppard drove with his wife, Monica, their daughter, and his mother-in-law to a rented cabin in the foothills of the Ozarks on the picturesque Little Red River, an hour from Searcy. He called it a much-needed last-minute getaway for the family, and for most of the weekend, it was.

Then, in the fading Sunday afternoon light, with his daughter and mother-in-law occupied in the cabin, Sheppard walked down to the dock with Monica and their black lab, Fluke. When Monica looked away, Sheppard helped the dog — always eager for a swim, just as he'd counted on — off the platform and into the Little Red River's notoriously deadly current. His wife looked back just in time to see Sheppard heave his own 300-pound frame into the river after their beloved lab.

Thrashing in the 39-degree water, Sheppard managed to hand the leash up to Monica, who hauled the dog to safety. But he struggled to swim back to the dock. Flailing desperately, he gasped that he was having trouble breathing. A moment later, as the current pulled him downstream, his head dipped below the surface and didn't reappear.

A frantic 911 call from Monica minutes later launched a search-and-rescue operation involving more than 60 people. Dive teams scoured the river, and a plane scanned the area from overhead. The next morning, Sheppard's shell-shocked coworkers brought their own boats up to help with the search. They found his fluorescent orange Eaton cap in shallow water not far downstream. But when 24 hours passed without another sign, the authorities abandoned — publicly, at least — any hope of finding him alive.

The urge to disappear, to shed one's identity and reemerge in another, surely must be as old as human society. It's a fantasy that can flicker tantalizingly on the horizon at moments of crisis or grow into a persistent daydream that accompanies life's daily burdens. A fight with your spouse leaves you momentarily despondent, perhaps, or a longtime relationship feels dead on its feet. Your mortgage payment becomes suddenly unmanageable, or a pile of debts gradually rises above your head. Maybe you simply awaken one day unable to shake your disappointment over a choice you could have made or a better life you might have had. And then the thought occurs to you: What if I could drop everything, abandon my life's baggage, and start over as someone else?

Most of us snuff out the question instantly or toy with it occasionally as a harmless mental escape hatch. But every year, thousands of adults decide to act on it, walking out the door with no plan to return and no desire to be found. The precise number is elusive. Nearly 200,000 Americans over age 18 were recorded missing by law enforcement in 2007, but they represent only a fraction of the intentional missing: Many aren't reported unless they are believed to be in danger. And according to a 2003 British study, two-thirds of missing adults make a conscious decision to leave.

People who go missing do so with an endless variety of motives, from the considered to the impulsive. There are of course those running from their own transgressions: Ponzi schemers, bail jumpers, deadbeat parents, or insurance scammers dreaming of life in a tropical paradise. But most people who abandon their lives do so for noncriminal reasons — relationship breakups, family pressures, financial obligations, or a simple desire for reinvention. The federal government's Witness Security Program provides new identities for endangered witnesses, but thousands of people who testify in lower-profile cases are on their own to face potential retribution or flee to a safer identity. So too are those trying to escape the unwanted attention of stalkers, obsessive ex-spouses, or psychotically disgruntled clients.

Starting over, however, is not as simple as it used to be. Digital information collection, location-aware technology, and post-9/11 security measures have radically changed the equation for both fugitives and pursuers. Yesteryear's Day of the Jackal-like methods for adopting a new identity — peruse a graveyard, pick out a name, obtain a birth certificate — have given way to online markets for social security numbers and Photoshop forgeries. Escapees can set up new addresses online, disguise their communications through anonymous email, and hide behind prepaid phones.

In other ways, however, the advantage has tipped in favor of investigators. Where once you could move a few states over, adopt a new name, and live on with minimal risk, today your trail is littered with digital bread crumbs dropped by GPS-enabled cell phones, electronic bank transactions, IP addresses, airline ID checks, and, increasingly, the clues you voluntarily leave behind on social networking sites. It's almost easier to steal an identity today than to shed your own. Investigators can utilize crosslinked government and private databases, easy public distribution of information via the Internet and television, and data tucked away in corporate files to track you without leaving their desks. Even the most clever disappearing act is easily undone. One poorly considered email or oversharing tweet and there will be a knock at your door. As missing-person investigators like to say, they can make a thousand mistakes. You only have to make one.

On the Monday morning after Matt Sheppard disappeared, Detective Sergeant Alan Roberson of the Cleburne County Sheriff's Office drove down to the Eaton plant to check Sheppard's employment record for emergency contacts. When Roberson arrived, the company was holding an all-hands meeting announcing Sheppard's presumed death. "There were a lot of people who were very affected by it," he says. After noticing discrepancies in Sheppard's employment record, Roberson spoke with the Eaton human resources folks, who told him that two weeks earlier they had alerted Sheppard to suspicions that he'd been misusing his corporate credit card. "That got me thinking," he says.

When Sheppard's body didn't turn up after another day, Roberson's curiosity deepened. He knew that Sheppard carried a company BlackBerry; his wife had told police it must have gone in the water with him. On Wednesday, Roberson asked Eaton to check for any activity on it. Sure enough, they discovered text messages sent after he had supposedly drowned. As far as Roberson was concerned, the rescue operation was now a manhunt.

The police subpoenaed AT&T — after Roberson's visit, Eaton had filed formal theft by deception charges against Sheppard, alleging that he'd placed more than $40,000 in personal charges on his corporate card — and the carrier tracked the messages to cell towers in the Searcy area. But by the time AT&T checked for the content of the messages, they'd already been purged from the system. Tracking the numbers texted from the phone didn't turn up anybody's account. Roberson concluded they were prepaid cell phones.

When he tried to reinterview Monica Sheppard, she'd retained a lawyer and refused to cooperate. A few months later, she sold everything and moved away with her daughter.

After that, Roberson says, "the trail went cold. We just flagged everything we could find." In March, the police conveyed their suspicions to the local press. Roberson contacted border security in case Sheppard used his passport and asked the IRS to watch for any W-2 filed with his Social Security number on it. When Monica took off without leaving a forwarding address, Roberson also contacted the local elementary school Sheppard's daughter had attended, asking it to get in touch if anyone requested the girl's records.

Tennessee specifically outlaws "intentionally and falsely creating the impression that any person is deceased," but strictly speaking, in most places there is nothing illegal about walking away from your life. Still, it's easy enough to run afoul of the law in the process of fleeing, whether through abandoned debts or identity theft. Insurance claims based on fake deaths — besides being illegal — are naturally frowned upon by insurance companies, who tend to pursue them to the ends of the earth.

New York City- and Texas-based investigator Steven Rambam has conducted several thousand missing-person searches over almost three decades. He made a name for himself in the '90s tracking down suspected Nazi war criminals in hiding. Sardonic and brash, with a thick Brooklyn accent, he has a knack for using technology to find people who don't want to be found. For Rambam, the proliferation of increasingly comprehensive data collection has been a boon. Even as anonymization technology improves, to the benefit of fugitives, "the ability to pull data from remote locations and cross-reference that data has increased even faster," he says. "So far the good guys are ahead, but maybe by a couple of inches."

To enhance his ability to search everything from DMV records to college yearbook photos, Rambam created his own investigative search engine and database, PallTech. It's so good that other licensed investigators and law enforcement agents pay to use it. Given a name, date of birth, and Social Security number, PallTech churns through hundreds of databases — collections of private and public records — and spits out up to 300 pages of investigative fodder like addresses, relatives' names, and aliases. It also enables elaborate combinations of searches, based on, say, a first name and month of birth. All of which helps investigators exploit the most common error made by people starting over: using details from their old lives in their new lives as a way to help keep things straight. "Whether it's transposing your social security number, your date of birth, or the letters of your name — that's the quickest way you're going to get found," says Robert Kowalkowski, a Michigan-based investigator.

There's also plenty of private data that makes your life easier — and your pursuer's, too. Take frequent flier accounts, Rambam says. "You get miles and convenience, and I get everywhere you've flown." Or Amazon.com: "The convenience of books delivered to your door, and I have all your addresses, at least one phone number, the books you read." PayPal and eBay: "Everything you've ever browsed: books to lamps, every address, people you've ever sent gifts to." (When Wired told him about the $5,000 contest to find the author of this piece, Rambam noted that he is working on a book about his experience using high tech tools to hunt down a friend.)

Exactly how investigators get that data depends on who is missing and the persistence of who is searching. Court-ordered subpoenas can give law enforcement — or private investigators hired onto the case — access to everything from ISPs to airline companies. Other times investigators may get more creative, scouring the runner's abandoned laptop or persuading a colleague to hand over an email that might contain a location-revealing IP address. They might enlist the public's help, using cold-case Web sites to spread pictures and collect tips.

There are also a few investigators for hire who are still willing to tread in dubious legal areas with tactics like pretexting, an age-old technique. Posing as the missing person, the investigator calls the phone company, cable company, or bank and uses a few of the target's personal details — and a measure of charm — to extract records from credulous customer service representatives. In recent years, Congress has strengthened anti-pretexting and computer-crime laws. But if your life depends on not being found, it's best to assume that your digital DNA is up for grabs.

People trying to outrun their old identities have to reckon not just with the data collected about them but also with whatever facts they've revealed about themselves. Facebook, MySpace, and Twitter are an investigator's gold mine, containing everything from your address books and photos (and, for a tech-savvy investigator like Rambam, what camera they were taken with) to your hobbies and favorite bars. A social profile that once would've taken an investigator weeks of on-the-ground work to build is a few clicks away. Minimal search-engine acumen — or an undercover account on a social networking site — can turn up a collection of friends for investigators to target, even if an online account is marked "private."

Generally, investigators work by building a profile of the person they are hunting and then waiting to capitalize on typical human frailties — poor memory, vanity, a craving for social contact. A few years ago, an investigator named Philip Klein was hired by Dateline NBC to locate Patrick McDermott, a onetime Hollywood cameraman who also happened to be Olivia Newton-John's former partner. McDermott had disappeared from a fishing boat in the Pacific, and the authorities presumed him dead. Early on, Klein likewise turned up only the vaguest hints that McDermott could be alive. "This was the ultimate walk-away," Klein says.

Then Klein decided to set up a Web site about the disappearance. Purporting to be asking for tips, it was designed specifically to trap visitors' IP addresses. Suspecting that McDermott was in contact with at least one confidant from his former life — and relying on the investigator's maxim that people on the run always monitor the pursuit — Klein blocked search engine crawlers from cataloging the site. He gave the URL only to McDermott's friends and family. Ninety-six hours later, it started registering multiple daily hits from an IP address in the beach town of Sayulita, Mexico. Klein says he eventually tracked McDermott around South America and contacted him through an intermediary. McDermott had a simple message for the investigator: His new life was "nobody's business."

Matthew Sheppard held his breath as long as he could, swimming underwater with the current until he was out of sight. Then he surfaced, swam to a dock, and pulled himself out. After retrieving a bag of clothes and $1,500 in cash he'd stashed the night before, he walked quickly down the road to a prearranged spot where a friend — the one person to whom Sheppard felt he could entrust his secret — waited with the car. They took off southwest toward the friend's home in Mexico, just south of the Rio Grande.

Two weeks before, when Sheppard sat down to formulate a plan to fake his death, he'd been armed only with Google and LexisNexis. Stumbling on an article about Steve Fossett, the explorer whose plane disappeared in September 2007 and whose remains were yet to be discovered, Sheppard concluded that even without a body, Monica would likely be able to obtain a legal determination of death and thereby collect his company-issued life insurance policy — worth $1.3 million. He pored over recent reports of missing persons and faked deaths, looking for strategies to emulate and pitfalls to avoid.

That, in fact, was how he'd come up with the idea of leaving his BlackBerry conspicuously at a gas station on the Friday before his disappearance. It was a classic misdirection: Someone would grab the phone and start using it, Sheppard hoped, and any cop who didn't buy the drowning would trace the phone to some petty thief — while Sheppard's real trail faded. (The ruse backfired, it seems, when the thief sent a few messages and then quit, convincing Sergeant Roberson that Sheppard was alive.)

Now, ensconced at his friend's house in Mexico and working nights as a dishwasher at a local restaurant, all Sheppard had to do was wait. He would monitor coverage of his disappearance, and once he was sure his wife had collected the insurance — the company had a year after his death to pay up — he would contact her and explain everything. She'd meet him in Monterrey, where he had already scouted out an agave plantation they could buy on the cheap. He'd spend the rest of his days making tequila.

But after two months, he started to get antsy. He missed his wife and daughter too much to wait. So, assuming that the authorities might still be logging Monica's incoming calls, he bought a prepaid phone, dialed her number, and broke the news that he was still alive. She was hysterical at first, alternately furious and overjoyed. She told him that he should turn himself in. But Sheppard, knowing he was already in too far, convinced her that they could make a new start.

The family reunited in Iowa, where they stayed at a motel. As the life insurance company stalled, they lived off the cash from Monica's sale of their Arkansas house and belongings. In Mexico, Sheppard had obtained an Iowa driver's license and Social Security number for one John P. Howard, to whom he bore a passable resemblance. Now he constructed a rèsumè around the identity, transposing his work history onto fake firms, and posted it online. For references he gave the numbers of prepaid phones. When prospective employers called, Sheppard pretended to be an HR representative and verified his own past employment.

Meanwhile, the stress of living on the run was taking its toll, and Sheppard had lost almost 70 pounds. After reading that the Arkansas police had contacted US Marshals about his case, he became wracked with paranoia. He would see cars parked at the defunct dealership across the street from the motel and imagine federal agents waiting to pounce. Remembering the blown escapes he'd read about online, he created a daily inspection routine for his car — turn signals, mirrors, taillights — to make sure the cops had no excuse to pull him over.

Eventually, "John P. Howard" landed an offer for a health and safety manager position in Yankton, South Dakota. The family packed up and drove west, where a real estate agent helped them find a rental house in a secluded area near a lake.

The family still kept to themselves, avoiding the local crowds on boating day at the lake. And Sheppard found it awkward responding to his new name, so much so that he asked his wife to start using it at home. But his paranoia began to recede. He even opened a bank account. It was starting to feel like they'd re-created a normal life — just the three of them and Fluke, their trusty black lab.

The fantasy of swapping out your tired life for a better one is a stalwart plot device in fiction, from Huckleberry Finn and The Great Gatsby to The Passenger and Mad Men. In such stories, the decision to take on a new identity often occurs in a single, serendipitous moment; an opportunity presents itself, and the character makes the fateful choice, often getting away with it. In real life, ad hoc escape plans rarely end well.

The most convincing way to disappear is to make people believe you are dead. And the most common locales for faking a demise are large bodies of water — places where a corpse might just sink or wash away, thus explaining a lack of remains. The chaos of a natural disaster, too, offers a tantalizing opportunity. Regardless of the diversionary method, the success of any stint on the run depends on a combination of advance planning and constant vigilance. "Most of them are not really going to take the time and energy to lay the groundwork to disappear," Rambam says. "For a lot of people it's an impulse thing: 'I can't take it anymore, I've got to get out of here, now.'" Take Samuel Israel: Convicted of fraud, the New York hedge fund manager in 2008 tried to convince authorities he'd leapt from a bridge over the Hudson River by writing Suicide is painless, the theme song from M.A.S.H., in the dust on the hood of his abandoned car. His plan apparently did not extend beyond parking an RV at a Massachusetts campground, and he turned himself in a month later. (Other times, there's just no accounting for bad luck: Australian businessman Harry Gordon, who faked his death in a boating accident in 2000, lived under a new identity for five years until the afternoon he passed his own brother on a mountain trail.)

Perhaps the most infamous recent faked death attempt, that of Indiana money manager Marcus Schrenker, involved a plan equally daring and bizarre. Accused of financial mismanagement, Schrenker, an amateur pilot, climbed into his Piper single-engine and set a flight plan for Destin, Florida. Flying over northern Alabama at 24,000 feet, he made a sequence of increasingly desperate radio calls to the nearest control tower, announcing that he had run into turbulence; that his "windshield was spider-cracking"; that the shattered glass had cut his neck; that he was "bleeding profusely" and "graying out." He then pointed the autopilot toward the Gulf of Mexico and bailed out with a parachute over Harpersville, Alabama. After landing, he made his way to a motorcycle he had stashed at a local self-storage unit.

Unfortunately for Schrenker, when two Navy F-15 pilots caught up with the still-airborne Piper, they noted that the plane was in fine shape — except for the open pilot's side door and empty cockpit. Even worse, Schrenker failed to put enough fuel in the plane to get it to the gulf. It crashed 200 feet from a residential neighborhood in northern Florida. In the wreckage, authorities found a campground guide minus pages for Alabama and Florida and a handwritten crib sheet with the bullet points "windshield is spider-cracking," "bleeding very bad," and "graying out." Federal marshals found him at a KOA campground in Florida two days later. Perhaps swayed by the additional evidence that prosecutors turned up on his laptop — including Google searches like "how to jump out of the airplane when parachuting" and "requirements to get a Florida driver's license" — he pleaded guilty in early June.

Sergeant Roberson got the call from the Searcy elementary school in early August. He quickly subpoenaed the school, tracked the request for the Sheppards' daughter's records to Yankton, and called the US Marshals. He knew it was still a gamble. "In the back of your head, you wonder: Am I wrong?" Roberson says. "Is he dead?"

South Dakota-based federal agents pulled up an address for the family and contacted the landlord. "I rented to that guy," he told them upon seeing Sheppard's picture, "but his name is John Howard." The alias led quickly to Howard's very Sheppard-like rèsumè, still posted on Monster.com. Then, in a scene befitting Sheppard's most paranoid fears, officers staked out the house, setting up in trees nearby, waiting for him to appear.

Sheppard was gazing out his back window at deer when he heard cars speeding down the gravel road toward the house and then the marshals bursting through the front door. His wife screamed, "He's not here!" but the agents found him a few seconds later hiding next to a bed. He didn't say a word.

In a rare study tracking people from the federal government's witness protection program that appeared in a 1984 issue of The American Behavioral Scientist, a psychologist named Fred Montanino outlined the difficulties of living under a fake identity. He determined that people were likely to feel "severe social distress" and "a pervasive sense of powerlessness," driven by the necessity of constant deception. "When the social fabric is torn, when individuals are erased from one part of it and placed in another," Montanino concluded, "problems arise."

Trading in your old identity and adopting a new one involves more than remembering an ill-fitting new name. It means a lifetime of duplicity that complicates every social interaction, lacing inconvenience and doubt into such humdrum tasks as registering a car or getting health insurance. "You do, to a certain extent, have to erase who you are," says Frank Ahearn, author of the guidebook How to Disappear. "Victims of stalkers have the motivation of saving their own lives. It's not as much of a — excuse my French — psychological fuck." But those looking to "pick up and live a palm tree lifestyle," he says, often "don't realize how difficult it is to start over."

A life on the run means enduring the intense isolation of leaving friends and family behind. "It takes an extremely dedicated person to forget everything in their past," says William Sorukas, chief of domestic investigation for the US Marshals, "and never make that phone call back to the family, not after 10 years go back home and drive through the neighborhood again."

Of course, technology can allow the kind of anonymous contact with friends and family that wasn't possible in the past. "Mom can have a phone under another name that only you call, or maybe you use encrypted email," Rambam says. "But somebody always makes a mistake."

Even in a world of cross-linked databases and location-aware phones, most people living on the lam are undone by complacency. "Do you have a hobby — are you a model train collector or a butterfly collector? Everything that defined your prior life, you have to stay away from," Rambam says. Yet almost anyone on the run comes to crave ordinary human contact. "When the newness wears off, you ask, 'How do I live my life?'" Ahearn says. "'How do I date? How do I not tell people about where I'm from?' People loosen up and go back to who they were."

And that's how most attempts to vanish end. A school registration, an email back home, a campsite guide with pages torn out. All mistakes look avoidable in hindsight, of course, and the nature of such stories is that only the failures surface. To succeed at disappearing is to never have your methods told. But for those who are caught, there's always the sour taste of what could have been.

Three months into his 10-year prison stint for theft and insurance fraud, Matthew Sheppard shuffles into the deputy warden's office at the East Arkansas Regional Unit on a sweltering summer afternoon. Clad in a baggy white prison uniform, he is 100 pounds lighter than when he went into the Little Red River. Sitting across from me on the warden's couch, he reflects on his tale in a subdued tone, tinged with relief. Even after his arrest, he says, "nobody ever sat me down and asked me the details" of the escape. (Monica, too, pleaded guilty for insurance fraud and was sentenced to six months in jail. Prosecutors accused her of being involved from the beginning, but Roberson says he isn't sure. Either way, she was technically guilty from the moment she learned her husband was alive.)

Looking back now, Sheppard himself has trouble making sense of it all. Today, none of his problems seem insurmountable, even the overcharged corporate credit card. He probably could have admitted wrongdoing and left the company, maybe even paid it back and kept his job. But at the time, "it felt like the whole world was on my shoulders."

After spending his early prison days laboring on outdoor work crews, he now works indoors handling the prison's construction contracts. He's hoping for a work release, maybe even with a company he worked with at Eaton. "I've been through the hardest time of my life; physically, mentally, with my family," he says. "I would settle for working at McDonald's."

He'd known the school registration was risky, and he wasn't surprised when I told him that was how the authorities had caught him. But he tries not to think too much about where he might be if only he'd kept his guard up a bit longer. "I don't see how I could have taken care of my family and kept my daughter out of all of this forever," he says. Mostly, he wants people to know he's remorseful for what he inflicted upon his coworkers, neighbors, and family.

By intentionally disappearing, Sheppard didn't relieve himself of his burdens — he just swapped them for another set. "What was worse?" he wonders now. "What I was dealing with when I did this? Or what I had to deal with when I was on the run?"

He does allow, on reflection, that a larger body of water might have made for a more convincing death. "That was one of the stupid things," he says, with a hint of laughter in his eyes, "that I didn't go to a lake or something."

Contributing editor Evan Ratliff (eratliff@atavist.net) wrote about dinosaur proteins in Wired, issue 17.07..