At the time, it seemed to be simply a “noble gesture,” as the novelist Walter Kirn writes in his new memoir, Blood Will Out. He agreed to drive a crippled rescue dog from Montana to New York and deliver it to an eccentric member of the Rockefeller family, who had adopted it on the Internet. Instead, the author of Up in the Air was pulled into a decade-long friendship based on an elaborate web of lies. Without knowing it, he had entered the world of a serial impostor and murderer. As he attends the trial of “Clark Rockefeller,” Kirn is forced to examine every interaction he had with the man, and the confounding way in which our notions of reality can be suddenly – irrevocably – stripped bare.

The trial of Christian Karl Gerhartsreiter, a German immigrant of many aliases, for the 1985 murder of John Sohus in San Marino, California, began in early March 2013. It was held in downtown Los Angeles, in the Clara Shortridge Foltz Criminal Justice Center, a hulking, rectilinear, gray hive of offices and courtrooms that stands across a plaza from City Hall. It's a part of the city that's rarely seen on film – a district of dismal bureaucratic towers presiding over an outdoor homeless shelter. Attorneys, jurors, and city workers mix on the sidewalks with shopping-cart vagabonds and lean, shirtless drifters squatting in ragged camps. (One morning I saw a man hunched beside his bundle tending a pet brown rabbit on a leash.) The lawyers walk briskly past the squalid scene, jabbering into blinking Bluetooth headsets and sip-sucking Starbucks mochas through plastic cup lids. The jurors appear vaguely stranded and at loose ends, uprooted from their routines and livelihoods. Certain blocks are lined with parked police cars and media vans equipped with satellite masts. Most everyone who can leave by rush hour does.

On the first day of jury selection, I rode an elevator to the Foltz Center's metal detector-equipped ninth floor, the home of the city's highest-profile trials – O. J. Simpson, Phil Spector, Michael Jackson's doctor – and took a seat on a hard bench only a few feet away from the defendant. I had known him for almost fifteen years by then and considered him a friend for ten of them, visiting him at his clubs and in his homes, talking with him often on the phone, and casually tracking his passage toward middle age while keeping him informed of mine. Except at the very end of our relationship, after his divorce from Sandy, when he came to me bewildered by an experience that I'd endured myself a few years earlier, we were never close friends, never intimates, but he was a singular figure in my life and a subject of frequent contemplation. I'd never written about him as I'd planned – my literary killer instinct had yielded to a desire for his favor – but I nevertheless imagined I'd understood him. Events had proved me wrong. They'd proved a lot of people wrong.

He was dressed the way he had been when I'd known him, as Clark Rockefeller (the name he also used with his attorneys and fruitlessly asked the court to recognize), in a preppy blue blazer, gray slacks, and a white shirt, every item a size too big. He still wore shoes without socks, exposing pale gaps of ankle, but he'd traded the thick black glasses I used to see him in for a professorial rimless pair. His hair had darkened to a mousy brown and his face was leaner than in the past, which emphasized the sharpness of his long nose and the elfin points of his big ears. According to the German passport found by investigators in a hiding place where he'd stashed various personal belongings, including several paintings rolled up in tubes and a book of signed blank checks from Sandy, whose salary had helped bankroll his charade, he had just turned fifty-two years old.

He'd been in prison for four years by then, the result of a prior conviction in Massachusetts for abducting his daughter, whom he called "Snooks," in 2008, during a supervised visit in Boston. I'd met her in 2002, when she was one, during a visit to his rambling country house in Cornish, New Hampshire. He'd lured me there with a promise to introduce me to J. D. Salinger, who lived nearby and was, Clark said, a friend. Later on in the trial that mad weekend would come back to me, reemerging in hindsight as the moment when all the clues were spread out for me to read and I should have caught him at his game, but for now my clearest memory was the child. She was learning to walk, I remembered. She stuck her arms out, toddling unsteadily toward a sofa where he sat coaching her, saying, "Snooks can do it." Sandy, who'd just returned from a long business trip, stood by looking haggard and angry. The child made the crossing. People clapped.

Clark snatched her when she was seven, off the street, bundling her into a hired SUV whose driver had been made to think that the pursuing social worker – who grabbed the car door and was thrown aside – was Clark's obsessed gay stalker. Several blocks on, Clark had the driver stop and caught a cab to a prearranged location where another dupe, a female friend, was waiting to drive him to New York City, supposedly to meet a yacht. (He paid her five hundred dollars for her services, apparently his customary rate.) From there, he and Snooks proceeded by unknown means to a house he'd bought in Baltimore, where he'd spent months preparing a new identity under the blandest of all his phony names: Chip Smith.

What he planned for his next move wasn't known; after a nationwide four-day manhunt FBI agents tracked him to the house and lured him outside with a staged phone call in which he was told that a catamaran he'd purchased was taking on water in the harbor. I had reason to think from a conversation we'd had a few months before the crime that he might have been headed for Peru, a country which he'd told me refused to extradite American parents who fled there with their children. This tidbit came up during one of the long phone calls that followed his divorce, when Clark would rant about Sandy's "cruelty" in separating him from Snooks. I was a divorced father myself by then and I sympathized with his frustrations, but now and then his intensity alarmed me. His mention of Peru as a safe haven was part of a troublingly transparent probe into my own potential willingness to act extremely in custody matters. Clark believed that the American legal system shamefully disregards the rights of fathers and that, as its victims, we needed to fight back.

The kidnapping, which made international news and later inspired a TV movie, exposed Clark Rockefeller as a fraud, the most prodigious serial impostor in recent history. It also connected him to a lineage older, and in a certain fashion richer, than that of the founding family of Standard Oil: the shape-shifting trickster of American myth and literature. In Melville's The Confidence-Man: His Masquerade, this figure takes the form of a mutating devil aboard a riverboat who feeds on his fellow passengers' moral defects. In Hucklebery Finn, he again stalks the Mississippi River as the Duke and the Dauphin, flamboyant mock aristocrats whose swindles are cloaked in Elizabethan claptrap. In The Great Gatsby he's a preening gangster sprouted from a North Dakota farm boy. In Patricia Highsmith's Ripley novels he's a murderous social-climbing dilettante. In Joseph Heller's Catch-22 he's Milo Minderbinder, the blithe wheeler-dealer who'd blow up the world if he saw a profit in it. He's the villain with a thousand faces, a kind of charming, dark-side cowboy, perennially slipping off into the sunset and reappearing at dawn in a new outfit.

But if Clark was all that (I'd learn after the trial that he understood his literary provenance and took great pride in it), then what was I? A fool. A stubborn fool. When his story began to unravel during the manhunt, and the Rockefellers claimed not to know him, I told a fellow reporter that they were lying, a family of cowards running from a scandal. I only backed down when his German name was published and the word Lebensraum echoed through my head. The disclosure unsettled me but it also softened me, especially when more facts about his background trickled out in the days after his capture. I too had a German name and German blood, and I'd spent a summer during college living in Bavaria, his home province. I was eighteen then, about the same age he was when, in 1979, two years before my stay in Munich, he left the small town of his youth for the United States. I'd left my own small town that year, for Princeton. I knew the yearning. No wonder we'd been friends.

Excerpted from Blood Will Out: The True Story of a Murder, a Mystery, and a Masquerade by Walter Kirn. Copyright 2014 by Walter Kirn. With permission of the publisher, Liveright Publishing Corporation.

This selection may not be reproduced, stored in a retrieval system, or transmitted in any form by any means without the prior written permission of the publisher.

This state of befuddled recognition ended when it was reported a couple of weeks after the kidnapping that Clark (the name Christian would never fit the slot; it lacked the snap I associated with him) had been linked through his fingerprints to a certain Christopher Chichester, who was wanted for questioning in a cold-case murder. The grisly particulars of the crime unnerved me: in 1985, John Sohus's corpse had been dismembered and buried in his mother's yard, where his bones were unearthed nine years later by swimming-pool excavators. Linda Sohus, the victim's wife, had vanished at the same time as her husband. Her body had never been recovered. Nor had police been able to locate Chichester, who'd been living on the property in a guesthouse rented from Sohus's mother.

Hearing all this, and then seeing Chichester's picture – it was a younger Clark in a tie and jacket, looking sly, with a one-step-ahead-of-all-of-you expression – I recalled a fuss he'd made once about his aversion to the sight of blood. It jellied his knees. It made his head swim. Like much that he said, the remarks came out of nowhere, unprompted and seemingly without a motive, just more of the colorful fog he spread around himself in what I'd diagnosed by then as a mild case of logorrhea, the compulsion to soothe oneself with talk, talk, talk.

On the day I relinquished my cell phone, keys, and wallet to the Foltz Center's hypersensitive metal detector, the shock of Clark's unmasking had not worn off. If anything, it had deepened over the years, combining with and compounding all the other shocks that I'd suffered since befriending him. The first, most savage of these traumas – the one that somehow stood for all the rest – occurred on the ranch, the day after my fortieth birthday. I was sitting in my blue Ford pickup, idling in the driveway near the house, about to fetch some hay bales from a field. Standing beside me at the driver's-side window was a friend from New York who'd flown out to help me celebrate. We spoke a few words as I put the truck in gear, and just as it rolled forward on its big tires, my friend cast a glance at the ground directly in front of me, a spot I couldn't see below the hood, and hollered, "Charlie!," the name of my one-year-old, who loved to crawl. The truck rolled on, a good ten feet–momentum. I stopped it as time elongated and yawned and I became a speck or cinder drifting in a nauseating gray void. I shifted into Park. I climbed down from the cab. Life had just ended for me, so I was calm. I hurried, because one must, but I was calm. With forty more years to absorb the ghastly image already taking shape in my mind's eye, adrenaline and panic were irrelevant.

He was sitting upright under the license plate, halfway between the rear tires. My perfect boy. The pickup's jacked-up, four-wheel-drive suspension had allowed the chassis to pass right over him. It made no sense. The overlay of horror – the scene that should have been – persisted in my vision as I reached for him. Angels. Providence. Only they made sense. In the realm of logic and causality, I'd killed my child, but love had vanquished physics and here he was in my arms, against my chest, with nothing but a pink patch on his forehead where the truck's differential had scraped the skin.

The accident sent a tremor through my life. Two years later I was divorced. I worked too hard. We'd never been a match. Mercury was in retrograde. Things change. Compared to what else can happen in this world, and to what almost had the day after my birthday, the divorce felt like business, a sad adult procedure. I'd married a teenager, what did I expect? To be the exception, as usual. Guess not. The sentimental turns to the statistical. I hung on to the ranch for a time, which seemed important, but cash ran low and I sold it to a neighbor who happened to be a real estate agent. A few days later he resold the place to a wealthy buyer he'd had waiting, pocketing a nice margin.

I saw my children – Charlie, and his older sister, Maisie – every other weekend, a schedule that makes a flip-card movie of parenthood. Sometimes they grew half an inch between our visits. I filled in the downtime with girlfriends and magazine work and wishful spasms of gym activity. Men who live alone don't live originally. We eat at the bar. We file for tax extensions. We call our worried mothers too often, no longer to spring exciting news on them – that season is over, and perhaps not missed – but to replay a skirmish with the ex-wife or get advice on what to tell a child who's been caught viewing hard-core Internet pornography. It's better, we think, than not calling her at all, and she must think so too, since she picks up.

Then one day she doesn't. In the summer of 2011, after a month of mysterious chills and headaches that she self-diagnosed as Lyme disease and treated with Excedrin and doxycycline, my mother died of an abscess of the brain. She was only seventy-one. She collapsed at her boyfriend's house in Iowa after a three-day visit to the State Fair. Her last meal was a snow cone. She lingered in a coma long enough for me to reach her bedside in Des Moines and, in the spirit of the living will that she kept folded in her purse, consent to the morphine drip that eased her passage. Because someone had told me the sense of hearing goes last, I held my phone beside her pillow and played her Bob Dylan's "I Shall Be Released." A day later, I drove to her house in Minnesota. In the center of her kitchen table, clipped in one of those little wire stands that florists put in bouquets to hold a card, was a note listing bank account numbers and names of lawyers. It was headed "If I die."

The cumulative result of all these shocks was to deplete some reserve of basic courage that I'd taken for granted since childhood. I wasn't so much depressed as chronically hesitant. Simple decisions that I'd once made thoughtlessly – whether to ask a woman on a date, whether to leave a front door key with a plumber, whether to answer a phone call from a strange number – felt loaded with uncertainty and peril. It didn't help any that out in Massachusetts, and then in California, my old friend Clark, under a foreign name, was wending his way through the criminal justice system, first for a crime he'd committed while I'd known him and that I hadn't seen coming but probably should have, and then for an older, more abhorrent offense that, the more I thought about our friendship, seemed coiled inside our interactions like a tiny, embryonic snake.

"Hitler went to heaven."

"The artist's blood."

I hadn't known him. I'd misinterpreted everything. Though it wasn't the harshest blow of the last decade, it may have been the most destabilizing, undermining my trust in other people and devastating my faith in my own judgment. Qualities in myself that I'd thought laudable – curiosity, openness, high spirits – suddenly felt like shortcomings or defects. "You can't cheat an honest man" goes the old saying, the notion being that falling for a charlatan requires moral softness in the victim. I had plenty of this, as I was well aware thanks to my upbringing in the Mormon Church. I lied on occasion, chiefly about sex. I could be two-faced around authority figures, kissing up to them while resenting them. At times I relished speaking caustically. And what I regarded as my trusting nature was, upon inspection, a kind of sloth. Instead of patiently working to get to know people, I'd decide that they were who I wanted them to be and discard them when they proved otherwise. This cycle of disappointment happened often. That it hadn't come close to happening with Clark – that he never diverged from my fantasies about him – should have been a sign.

Another symptom of my spiritual laxity was the Ritalin I was taking when I knew him. Its effect was to grant me cheap energy on cue, and thanks to the way I was living and working then – juggling deadlines, ranch chores, and young children – my demand for cheap energy was vast. The cycles of euphoria and exhaustion induced by the drug caused many skids and stumbles. I squandered thousands on online trading sprees. Buy Lucent Technologies at 28, sell in a sweat when it dips to 26, rebuy at 27, watch it rise, double up when it spikes, freak out when it ticks down, sell half, sell all, buy Apple, and on and on. I ordered a car once in this scrambled state, leaning in next to the salesman at his computer and choosing options that showed up on his screen as a morphing animated vehicle that kept changing colors because I couldn't pick one. Maybe the pills were one reason I bought Clark. The mood of promiscuous readiness they roused was indiscriminate and undiscerning.

Or maybe my egotism was a homing beacon. Maybe it made me a more attractive mark. Our history ran both ways, a partnership, meaning that whatever I'd seen in him, he had also spied something in me. These characters read you, according to the books, and all the time they're talking, they're really listening, alert for pings and echoes. They use sonar, not questions; Clark never asked me questions. I suspect that one quality he tuned in to early on was my collaborative listening style. Instead of shrinking from his loopy stories, I helped him refine them by teasing out their details and nudging them toward heightened vividness. It's one of the services Nick performs for Gatsby, consolidating his fabricated self by playing the role of ideal audience.

Clark would also have felt my eagerness not only to trust but to be trusted. He'd told me in our initial phone call that his plane was in China with his wife, and yet there she was when I arrived. I don't recall him explaining this inconsistency. I do recall noting it and saying nothing. What is it in people, or just in people like me, that would rather let a lie go by, would rather wish it away or minimize it, than point it out and cause the liar embarrassment? Why would we rather have someone see us naked than see someone naked? Politeness, I'd always thought. The essence of politeness is feigned blindness. But Clark knew otherwise. He knew that my choice to spare him the slightest shame, to view him as he wanted to be viewed, stemmed from a selfish craving for an alliance. I would blink when he stumbled, go deaf when he misspoke. He could count on me.

I'd come to Clark's murder trial with many questions, beginning with why I'd once found him so impressive and how, in instance after instance – some of them still in the process of resurfacing – I could have been so stupid, so obtuse. I also wanted to learn how his pretensions might be related to a violent nature (if Clark even had a "nature," a larger question). But there was this, too: I'd come to finish a story, the one I'd considered writing when I met him but later abandoned in deference to our friendship.

I still remembered where I was when I ruled out using him as a character, even in fiction. The Lotos Club on East 66th Street is a quietly posh refuge for Manhattan's cultural elites. Mark Twain was once a member. He called it "the ace of clubs." Its manicured furnishings and forgiving lighting brought to mind an exquisite funeral home or a faculty club for learned ghosts. We sat in high-backed chairs that afternoon, the focus of a grudging, aging staff whose loathing for us was obvious. He was drinking a gin and tonic. I had a Coke with lemon. I don't recall the topics we discussed, but they probably touched on global politics and his arch-theme of Western decadence versus Asian drive and discipline. Behind his chair was a portrait of some dead worthy gazing immortally into a future that the man appeared confident of shaping. Perhaps he had; I didn't recognize him. My hunch was that this would not have bothered him, since men of true influence operate offstage.

I wanted to be invited back – I liked the club's effect on me. I liked how it made me hold my glass, not wrapped in my hand and snug against my palm the way I'd hold it in a restaurant but lightly, with precise, prehensile fingertips. I also liked how comfortable I felt, sitting askew on my cushion, head tipped sideways, thumb on cheekbone, ankles crossed, mirroring the flow of Clark's remarks with adjustments of forehead tension and chin position. I wasn't the lone Princetonian there, I sensed. I doubted that I was the lone Oxfordian, either. Was that my old roommate's father in the striped tie? The wrinkles across the insteps of his brogues were exactly the ones I wanted on mine someday. Montana – I may have erred there. Too far afield. Perhaps it was time to move back to the center. ("I think you nailed it, Clark. I really do. I suspect that's what most people think but never say.") We made an interesting pair, the small-town novelist and the lonesome Rockefeller. I brought him news of the people, the human ruckus, and he brought me news from the Olympian eagle's nest. ("I think I'll switch to club soda with a lime. And you can take these nuts. We're done.") He envied my mobility, my freedom; I coveted his security, his ease. What was funny was how protective I felt toward him. What was nice was how safe he seemed to feel with me.

These memories struck me as absurd now, a ridiculous, disgraceful capitulation. I'd bowed to a tinfoil prince. I'd kissed his ring, and the irony was that the true ring was on my hand. The only Ivy Leaguer there was me. The only Lotos Club type was sitting in my chair. I'd had it all backwards, upside down, reversed. I, the fawning aspirant, should have been the one conferring status – and I suppose I was, in some sick way. Clark must have loved it, watching me degrade myself. Worse, though, I was degrading my vocation. My grant of literary immunity to the strangest creature I'd ever met violated my storyteller's oath. Writers exist to exploit such figures, not to save them. Our duty is to the page, not the person.

The trial was my chance to right all this, to call off a deal I shouldn't have agreed to and hadn't been asked to agree to, come to think of it. I'd made the deal unilaterally, with myself, hoping that he'd reward my generosity. No more of that. The trial meant Clark's story was reaching a conclusion; if I hoped to catch up with it and make sense of it by exploring its intersections with mine, the time was now, the place was here. Two basic outcomes were possible, and two morals. If Clark were found guilty, Abe Lincoln would be proved right – you can't fool all the people all the time – and I would be present to savor his comeuppance and participate in my own redemption. If he were found innocent, however, the tale would end on a warped, postmodern note, and Clark might well emerge as a celebrity, proving the world was a bigger dupe than me. I felt prepared for both contingencies, but I feared that the second, limbo, was more likely.

The name of the case seemed to foreordain a muddle: "The People of the State of California, Plaintiff, vs. Christian K. Gerhartsreiter, aka Christopher Chichester, aka Christopher Crowe, aka C. Crowe Mountbatten, aka Clark Rockefeller, aka Charles ‘Chip' Smith." The nature of the jury concerned me too. Its members would be drawn from the same neighborhoods that supplied the bumbling O. J. Simpson jury. The word from the old hands around the courthouse was that downtown LA jurors shared a reflexive suspicion of authority and a frank dislike for the police. I'd also heard rumors of their scorn for circumstantial evidence, which TV crime shows supposedly had taught them was inferior to smoking-gun stuff such as trace DNA and microscopic fibers. If indeed this prejudice existed, it would favor the defense; I happened to know from pretrial publicity that circumstantial evidence – really just an incriminating story about Clark's peculiar behavior before the murder and his evasive behavior afterward – was almost all the prosecution had.

The process of choosing this jury went on all day. Waiting in the hallway outside the courtroom, the pool of a few dozen prospects blended well with the associates of local gang lords whose trials were taking place in the same building. Not one of the candidates resembled Clark or someone he might have relaxed with at the Lotos Club, but many of them had the class and ethnic markers of "service people," the folks he'd probably engaged as cleaners and gardeners. The euphemism that sprang to mind was "urban." One middle-aged Latino man with a lordly stomach, a curled, waxed mustache with twisted points, and a sizable tattoo partially visible above his collarline, wore his straw hat and dark shades into the courtroom when the bailiff called his name. "Clark's defense will definitely want that guy," whispered Frank Girardot, the editor of the Pasadena Star-News and a veteran trial reporter who'd covered the Simpson case. Girardot was right; the big fellow made the cut.

Judge George Lomeli worked his way through the long procession of candidates, many of whom spoke halting English, while others seemed past their prime as alert, analytic intellects. Lomeli appeared well-suited for the case, a handsome man with a sharp but genial manner that combined authority and wit and even a hint of debonair Old Hollywood. He looked good in his robe, which matched his hair and mustache, and he appealed to the candidates' sporting sides by promising an "interesting" trial. Lots of folks tried to beg off anyway, citing work conflicts, family difficulties, and religious holidays. Of those who seemed most inclined to do their duty, some appeared to have little else going on. This bothered me. If I, the Princeton and Oxford graduate, had fallen for Clark's ingenious stratagems, how would these people penetrate the veil? With some jurors, I feared a culture clash. I'd seen a list of the prosecution's witnesses, among whom were several white-shoe finance types who'd known Clark in his late-1980s guise as Christopher Crowe, a hungry Wall Street bond guy. The working-class jurors might find these smoothies baffling, or loathe them on sight. Would it matter? No idea. I'd never attended a murder trial before. I'd certainly never had a stake in one.

My stake in this one was hard to formulate. The harm Clark had caused me wasn't grave enough to instill a lust for vengeance, but I hardly wished him well. The murder aside, he had a lot to answer for, and the trial was likely to offer him many rebukes, even if it spared him the ultimate one. Gratifying and fascinating viewing. I hoped my time here would educate me, toughen me. Having been beguiled by his magic show, I would now be able to go backstage and see the tricks he'd played explained. "That Walter Kirn is one shrewd judge of character"–this had never been said of me. Maybe the trial would wake me up.

As the potential jurors faced the judge, Clark turned around and watched them from his chair. Now and then he'd offer them sad smiles, affecting sympathy for their complaints, but mostly he wore the detached, attentive look of an anthropologist in the field. Who were all these people, so many of them so brown? What was this ritual unfolding around him? I'd never seen a German look as German as Clark did when he assessed his likely assessors. His eyes were like small blue coins behind his glasses. One sockless foot tapped away beneath his chair. In his right hand he held a pencil stub poised above a yellow legal pad. I'd heard he'd been writing a novel while in prison, a multipart epic of European politics that began at the close of World War One and ended in the 1960s. It was competent but dull, I'd heard, well researched but inert.

That Clark was guilty I had little doubt. Twenty-eight years ago, here in California, he'd killed his landlady's adopted son and his life ever since had been a masquerade. The trial would permit the prosecution to color in and substantiate this story, but I already knew it in outline and found it credible. What I didn't find credible anymore was me. When I'd learned that Clark might be a murderer and instinctively found the notion plausible, the effect on me was Galilean. It humbled me. It reoriented everything. It revealed to me the size and power of my ignorance and vanity.

About two hours into jury selection, while scrutinizing another would-be juror, Clark glanced to the side and saw me sitting there. I nodded at him. I thought he might nod back. I was, after all, a face from better days. He sneered at me instead, arching his eyebrows, wrinkling his nose, and twisting up his lips into a horrible, prissy little knot. The look was vicious and contemptuous and indicated that he viewed my presence as a betrayal of our relationship, as conduct unbecoming a gentleman. I viewed things differently, of course. To me our relationship was the betrayal. Nor did I care anymore to be a gentleman.

For the rest of his trial, until we met again, he pretended that I wasn't there.