"People need to be naughty," I told my mother recently. She was aghast at a current scandal: the senator and the page, or maybe the lawyer and the little girl, the priest and the altar boy. I wasn't shocked; appalled, yes, but not mystified. I don't pardon the behavior, but I think I understand it. My mother adamantly didn't. Doesn't. That's where I find my father, in whatever private legacy I can claim. I know that he, too, understood a doubled existence, the one riding the surface, and the one operating underground. He would have labeled it privacy; he believed ferociously in it. In his last years, he explained his dementia to me once, saying that he was aware of its presence, that he had the obligation to operate fully inside the real world that we, his family, could perceive and that we shared with him, and then he also had the obligation to keep straight another world, one utterly clandestine and thoroughly his own. He knew it wasn't real -- not to us, anyway -- and yet he also knew he had to function within it, since it was his. The fact of these competing worlds seemed like a version of the secret life he'd always led, one designed in the imagination, enacted in darkness, with elaborate rules but not the usual ones.

The onset on adolescence surely is the crudest version of a doubled existence, the dueling forces of childhood and adulthood awkwardly, publicly, battling for position in a single body. My own teenage years coincided with the emergence of a serial killer in my hometown, Wichita, Kan. Just nine days after my 13th birthday, an occasion I can recall mostly because my three brothers would not stop staring at my suddenly transformed chest, the killer claimed his first victims.

The family he killed lived in a house across the street from my grade school, and a few doors down from one of my friends. I could easily imagine the inside of that house, since I'd attended a birthday party at my friend's home, which shared the same basic floor plan. I could also imagine the route the killer took after leaving the four bodies in the house, down Edgemore to Central, Central to Oliver, where he abandoned the victims' station wagon in the Dillons Market parking lot. Is it only a 13-year-old's tendency to be thrilled by the seeming proximity of such horror and unspeakable grotesqueness? Was my vicarious rapture, and ensuing guilt for it, solely the purview of the awful self I intuited lurking inside me?

That Dillons was where we always went during our lunch hour to buy candy. Buy it or shoplift it. I knew that parking lot well.

The family he killed was named Otero. There were five children, and two of them were home when he struck. The others were at school, two in junior high, one in eighth grade and one in seventh, like me, and at the same school. Danny and Carmen Otero were the ones to discover their dead parents and siblings, when they returned home after school. It was January; I could imagine their trek, that awful gray day, along Oliver, probably across a shortcut in a canal, and no doubt passing the Dillons where their car was parked in the lot. Would they have noticed the car? Gone through the grocery's automatic doors hoping to find their mom inside shopping, maybe talk her into some junk-food treat At the very least, ride the rest of the way home?

I didn't know the Oteros. But I knew the world around them. I knew from the newspaper that the parents had been killed first and that the little daughter, hanged on a basement water pipe, was found with semen on her socks. She and her murdered brother, the youngest, were near in age to my own little sister and brother.

It was months later that the killer began crowing about his escapades. He was provoked by published news that someone else claimed to know who had killed the Oteros. He wished to set the record straight. "Those three dude you have in custody are just talking to get publicity … I did it by myself and with no oneshelp [sic]" his first written overture began. He then assigned himself a name, the BTK, which stood for Bind, Torture, Kill -- a signature, ownership. This stubborn need of his to be correct -- to be the authority on the subject of his work -- would prove to be his eventual undoing. When he was finally apprehended, 30 years after his first kills, it was because of the same impulse to notify the media that they'd once again gotten the story wrong. Only he, the man who'd literally gotten away with murder, was qualified to set the record straight.

He didn't fully set it straight until he confessed, at length, in 2005. Until then, his "reign of terror" had seemed to be in direct correlation with the years of my own adolescence, from 1974 until 1978, a period of time I'm sure my family would also have called a "reign of terror." And then, at just about the same moment, we both had disappeared from Wichita -- I, mercifully for all parties, to college, and he to silence.

But during those peculiar years, the BTK strangler continued to strike. Across the city, citizens entered their homes by first checking for phone reception (he was known for severing the wires), and wielding baseball bats. They installed burglar alarms. Ironically, the man who installed many of those devices was the BTK himself, aka Dennis Rader. By day, ADT Home Security workman; by night, stalker and murderer. His victims appeared in the newspapers, his taunting missives showed up on the KAKE 10 o'clock news. He was a freakish fact of my adolescence, a menace lurking in the city, an actor who required an audience. Our paths crossed curiously; perhaps everyone in Wichita felt the peculiar overlap with one or more of the victims of his crimes. BTK continued his bizarre game playing with the media, either before or after killings or attempts, on one occasion notifying the police from a pay phone of the murder he had committed hours earlier. He referenced peculiar details, mentioned esoteric characters, quoted archaic sources. A few of those quotations seemed to have come from song lyrics mimeographed for an English literature class taught at the local university, Wichita State University, and its professor, P.J. Wyatt was a good friend of my parents, who also taught there, and in the same department. To me, this woman was just another of their many professor friends before she held a specific role in the dirty city drama.

I could imagine that woman, too, as she'd been seated in our kitchen plenty of times, drinking wine, eating cheese. I'd sat listening to her just like the BTK had. Maybe he'd thought similar things about her hair or wardrobe or sense of humor. Maybe he'd guessed correctly about her sexual orientation.

In high school, my friends and I made some unusual acquaintances over the telephone. During one of our conversations, one of those endless teenage girl conversations, we suddenly could hear another conversation on another line. "Crossed wires," it was called, I guess, and we listened hard to make out what the men were saying. They were discussing bongs and kegs. They were planning a party. We shrieked at the top of our lungs until they heard us, too. We arranged a meeting, the four of us on our crossed conversations; putting ourselves at risk was instinctive. The urge had arrived with the other baggage of adolescence.

Only one of the men showed up. Lyle. A slacker, a loser, a complete disaster. But we couldn't have been convinced of that. He was better for having been found over the phone line, whispering there like the devil in our ears. We attended. We met his dope-smoking friends, men who hadn't finished high school and certainly weren't going to college. Eventually, they would find jobs, shave their scraggly beards, quit selling weed and start selling, say, weedkiller, down at the Ace. But for now, they were our dark secret, our attractive nuisances.

They believed we were in college. They believed we were of age. They believed we were idiots for thinking so highly of them, as no one their own age would give them the time of day.

We met them sometimes at the Cedars, the bar where we flashed our fake ID's. Located maybe a mile from my house, it was a bar where men outnumbered women 10 to 1. I parked around back, since my parents' graduate students lived in the neighborhood and I didn't want the car recognized. Also in that neighborhood had lived Kathy Bright, another of BTK's victims, killed a few months after the Oteros. Her place wasn't far from the bar. He could easily have been among the lone men who were always at the Cedars; when he was later caught, he confessed that he'd first spotted her picking up her mail, something he could have done from the bar's parking lot.

He could have been sitting in the parking lot, alone in his car; he might have been there a few years later when my friends and I would leave high school in order to have a liquid lunch at the Cedars instead of East High cafeteria fare. Our own sense of irony was to sometimes sneak into the Fraternal Order of Police Bar, in downtown Wichita. There we imbibed with the cops, we under-age and welcome, they delighted, the F.O.P.'s man-to-woman ratio even more disastrous than the Cedars'.

We loved getting away with this. The layered assaults on the trust placed on us -- by parents, teachers, employers, cops -- was exhilarating to thwart, intoxicating to betray. We were our own secret order of scamps, thrilled to goad one another into more and more dangerous situations. The pilfered cocaine from the drugstore where one of us worked. The night spent with the strange man who lived at the library. Our fourth member, an imaginary figure who mail-ordered pornography and failed to pick up pizzas held under her name at Godfathers, where two of us waitressed. She also made prank calls to the college dorms. None of these shenanigans was fully finished until we'd shared them with each other, perhaps bragged about them at school, stood at our lockers hungover and notorious, worrying our honors advisors, frightening the freshmen.

Wichita was never exciting enough for us; perhaps no place ever is, for teenagers. My friends and I entertained ourselves by following cars wanting to see what would happen. We chose cars occupied only by a male driver. Around town we would follow this man, turn when he turned, stop when he stopped. Occasionally, that man ahead of us would notice. Mostly they seemed flattered, amused, perhaps perplexed. Only once do I remember our feeling in any way threatened by the driver. Like those crazy crank callers in the 1965 movie "I Saw What You Did," we chose the wrong target, a man paranoid enough or maybe just having a bad day, who grew tired of our antics and jumped out at a light, roared toward us shaking his fists, infuriated. Fortunately, that day my friend was borrowing her step-father's Trans Am, and we squealed away.

Adolescent rebellion accounts for my and my friends' schizophrenic lives; we felt a need for adventure, misbehavior, a stretching of wings and overstepping of boundaries, an enactment of fantasies. We felt impervious to the antics of someone like the BTK; we called him the BLT. Like us, he wished to be infamous, feared and admired.

The two-sided nature of a person (the ability to have two lives, and thereby double the small measure provided us) must be what inspires such feverishly enamored fans of superheroes. Who wouldn't want to have their traits? Ordinary by day, possessing great powers by night.

My father had his own secret, second life. He wasn't a superhero, of course, more along the lines of do-no-harmer by day, do-kinda-bad by night. His misdeeds became apparent to me at a time I was conducting my own, perhaps only because of that fact. A waitressing friend of mine had seen him at a hotel bar with a redheaded woman. Once, just as my mother's car was pulling from the drive, she on her way to a night class, the phone had rung in our house. I picked up upstairs at the precise moment my father did downstairs. The woman on the line murmured things. My father soon after left the house. "Errands," he called them, his departures and absences. He was frequently running them. These rumors, the speculation built around them, fueled my own sense of what awaited in the adult world, one that appeared to have a secret basement beneath it, some nocturnal habitat accessed by trapdoors and transfiguration.

Everything had two sides, it suddenly seemed. The bathroom, for instance, that exquisite chamber of secrecy. Lock the door, open the window, run the bath. Smoke a bowl while soaking in hot water. And after? The shampoo, the Visine, the toothpaste, the perfume: all readily available. In the toilet tank two airtight pickle jars, pipe and pot stored for next time. Also handy at our house was the perennial presence of some sad-sack grad student or relative down on his or her luck, camping in the attic, sleeping in the basement, leaving random evidence of despair here and there. "Blame it on Hannelore," was our refrain for the year the German artist was hanging around. She made delicious mashed potatoes when it was her turn to cook; she also left hypodermic needles behind the hamper.

Not only people and rooms, but objects took on second lives. The Jeep that had, over many years, been the Teenagers' Vehicle, not only transported my brothers and me to work or school, but also into the country to parties. Once, through the plate-glass window of our local Mexican fast food stand, Taco-Tico. More than once conveying us out into the night, to the bars and apartments and empty lots in which we lived our own secret lives.

Returning home one night, having worn panty hose beneath jeans, I woke to discover the hose cut off at my thighs. Very slight nicks in my flesh where some device had been manipulated. Box cutter? Toenail clippers? Teeth? That darkness seemed to me the very hallmark of adolescence. My first kiss, when I was 15, took place on the same night as my first alcohol blackout.

Maybe Wichita expected the BTK to turn out to be as compelling as the most famous real or fictional serial killers, but they would be disappointed. The man who was finally caught was a good Christian neighbor, the least likely suspect, the man next door who was deacon at his church, leader of Boy Scouts, longtime husband and father. He routinely circled the neighborhood in his official duty as codes enforcer, pointing out violations and issuing citations -- for overlong grass, for example, or cars parked in front of driveways, picayune infractions, over-zealotry about rules one of his abiding daytime traits. He was like Dennis the Menace's grumpy next door neighbor, Mr. Wilson. He even resembled Mr. Wilson, with the scowling brow and mustache. His name was Dennis Rader. He was also BTK. He had a job installing security systems. He had a hobby of evading those same systems. He had children; he killed children. He wore a city-provided uniform; in secret, he dressed in women's underthings, knotted himself up with pantyhose and handcuffs, and took photos.

You could be shocked by such a thing -- his murders are shocking, no two ways about it; he bound strangers, tortured children, killed 10 people. Those are the horrors he committed, and all without any apparent logic, no particular vengeance, no special grudges, nothing personal. And still, what seems most shocking is the identity, the final piece of the puzzle which is that he was living among us all along, an ordinary curmudgeon. In other words, it could have been anybody. He didn't have to look or act like Charles Manson. He could look and act like Mr. Wilson. And that's what interests me most. There my friends and I were, after all, ordinary teenage girls, going to school, making good grades, walking our dogs, baby-sitting our siblings.

And driving drunk, rendezvousing with strangers, pursuing unknown men, stealing grandma's pills, sleeping with our teachers, shoplifting. Waking without knowing exactly what the other self had gotten herself into.

"Factor X," the BTK named his obsession; TV's favorite serial killer, Dexter Morgan, calls his secret urgent need his "dark passenger." My father's secret life exacted a price, in our family; he and my mother were divorced the year I got married, then remarried the year my daughter was born. His dementia, late in his life, oftentimes produced a word-salad that only his intimates could have deciphered, confession and guilt and paranoia, those two lives of his conflated in some mysterious manner, battling for mastery of a single self. For myself, Factor X, my own dark passenger, evolved into the writing of fiction. That world, of make believe and danger, of posited selves and extreme outcome, has satisfied an urge in me for mayhem and disruption, of pushing past conventional wisdom and conformist morality, for high drama and disaster and absolutely black, bleak fantasies. To author it, and to expose it, both. To create worlds in which the awful human attributes are insistently aired, and then to claim credit for having exposed those worlds and traits. "Cute kids," I might say to my neighbor and his tow-headed twin boys. Hideous life, the narrator of my fiction is simultaneously thinking, ready to commit something awful on the page.

Antonya Nelson is the author of nine fiction books, including the short story collection "Nothing Right," and her newest novel, "Bound." Her works have appeared in the New Yorker, Esquire, Harper's, Redbook and many other magazines, as well as in anthologies such as "O. Henry Prize Stories," and "The Best American Short Stories." She has received a Guggenheim Fellowship, an NEA Grant, the Rea Award of the Short Story and, recently, the United States Artists Simon Fellowship. She lives in New Mexico, Colorado and Texas.