By John Sedgwick

JULY 31, 2000:  The car's a silver Audi, with a Massachusetts plate that ends JB, and it's dead ahead of me on Beacon Street as we pass through Coolidge Corner. I've been following it since Chestnut Hill. Staying right on it, in fact; going where it goes. And I've gotten to know JB a little. The windows are tinted all around, so I can barely see in. But I can tell that the Audi is occupied only by the driver, and a slight bushiness to the brown hair visible above the headrest suggests that the driver is a young woman.

It's a kind of dance we do, the two of us. She leads, I follow. I stay close enough not to lose her, but not so tight that she'd sense my presence. Now, as she hurries down Beacon, she hooks a sudden left onto a side street. I stay with her, my headlights brightening her rear-view mirror as we weave through Brookline's back roads, past joggers, pedestrians, police cars. No one pays me any particular notice, and why should they? Mine is just another car on the road.

The streets turn quieter, trees arc overhead, the houses rise in price. Finally, her taillights flare -- a seductive reddening that pierces me -- and she slows, trolling for a parking space, finds one and backs in. I drive by slowly, craning my neck for a good look at her. She is in her late 20s, with features that suggest some sophistication. A slim necklace curves around her neck; a jewel hangs from her ear. I peg her as a young professional, an architect maybe, with a bit of style. I pull over a quarter of a block down, watch her through the rear-view, my motor running.

She emerges from her car, smoothes out her skirt. Why, I wonder: is she about to see someone? Without noticing me, she heads across the street. She mounts the stairs of a small frame house, pulls out a key that she fits into the lock. She opens the door, passes inside to the unlit interior, shuts the door behind her. I click off the engine, step out of my car. I glance about, see that no one is watching. I quickly cross to the sidewalk by her house, my sandals slapping against the pavement. I feel myself pressing against something that's more than air as I approach her front steps, gaze up at her house. The windows are open to the street, the filmy curtains sway in the breeze . . .

I'm not a stalker, in case you're wondering. I'm a novelist. After more than 20 years of magazine journalism and an occasional nonfiction book, I switched over to the other side and wrote a psychological thriller about a man named Rollins who likes to follow people in his car. He's the stalker, you might say. Except that he, too, would resist the term. He is simply curious. As he tells a young female colleague who tries to befriend him, "Haven't you ever wondered about people? What they . . . do?" To get some answers, Rollins takes to the road to tail people, tape recorder in hand to keep a record of what he sees.

Why did I get so involved with a crypto-stalker? Because he was a version of me, I suppose. All journalists are stalkers of a sort, pursuing their quarry. And I'd done my share of watching and waiting. But I also sensed -- long before the shows Big Brother and The Real World made this thought a commonplace -- that a voyeuristic relationship to the world was gradually becoming the norm. As Rollins peers out through his windshield, he is simply dramatizing the strange new detached engagement, for lack of a better term, that is now nearly universal. Virtually everyone now stares at life through one screen or another, right? Rollins takes to the road; we cruise the information superhighway. But I regarded his detached engagement only as a place to start, and I'd like to think that Rollins is gradually humanized as the tale proceeds. He comes to understand why he is the way he is, and he struggles to do something about it.

Curiously enough, I'd never actually tailed anyone in my car myself, and I didn't feel the need to do it for the book. Years ago, I used to go out on surveillance with Gil Lewis, a local private investigator who became the subject of my first nonfiction book, Night Vision. I'd ride with him as he tailed errant spouses, or an occasional murder witness, in his Toyota Celica, a Muriel Coronella going between his jaws. But no, I never actually went out driving. Partly I was chicken, of course. I didn't want to be embarrassed -- or arrested. Also, I wasn't sure that I could stay with a car all that successfully. But I suppose the real reason was that the pursuits -- as Rollins terms his nocturnal rambles -- were something my character would do; they weren't something I would do. And I needed to believe there was a difference.

Now that the book is done, however, I've reconsidered. After my years with Rollins, I too have grown curious about those seemingly anonymous cars out on the road -- what they're up to, where they're going. And it occurred to me that by spending an evening or two out "Rollinsing," I might make a last contact with my beloved protagonist before bidding him a final farewell.

AND SO I went. Armed with my own little Panasonic, I started out tailing cars around my house in Newton, then branched out. The first thing I discovered is that it's pretty easy to tail a car. Having followed a few dozen for distances ranging to nearly 30 miles, I can say with some assurance than none of my subjects have had a clue I've been on them. This, indeed, is a large part of the pleasure of the tail. It's one of life's few relationships that are purely one-way. (The only thing that comes close, possibly, is celebrity worship, although in that case the stars -- Britney Spears, Mark Wahlberg, et al. -- are obviously putting themselves out there for all to see: each one an exhibitionist as perfectly suited to the nation's voyeurism as a wall socket is to a plug.)

Enclosed in their seemingly impregnable bubbles of glass and steel, the subjects of my pursuits are convinced they're putting out no signals whatsoever beyond the indicator lights for left turns or right. It may be, in fact, that the car is the last place to offer at least the illusion of such privacy. Houses are thoroughly wired these days, and offices -- forget it. Even with cell phones, people think of their cars as their own private shower stalls. From what I've seen, I'd say most drivers can't imagine that anybody is looking. Lots of times they're singing away, or bobbing their heads inanely to rhythms only they can hear. And, especially in Boston, they often drive as if nobody else were there, too.

In my novel, Rollins likes to follow people back to their houses, to pin these drivers down to a particular locale. That's a lot easier to do in the suburbs than in the city. I made a point of going out at dusk, so that the gathering darkness would reduce me to just another pair of headlights on the road. At that hour, most everyone in the suburbs is heading home, and I tailed any number of people back to their front doors, the suspense mounting right up to the moment they entered their dark houses with (often) take-out in hand. Eerily, the very first car I tailed led me to a house across town that looked remarkably like the house that Rollins, in my book, returns to -- the one that becomes the Dark House of the title. I even went back there a few times, to check out the neighborhood and see what I could pick up about that Dark House's inhabitants. I stayed in the shadows, watching. But, oddly, I never detected any sign of life. It was as if the garage had swallowed the driver whole.

Still, nosing around that street, I discovered the demographic truth that marketers have long known perfectly well: cars fit houses and houses fit neighborhoods. So Mercedeses, for instance, invariably end up in what I came to think of Mercedesvilles, where there are Mercs galore. Volvos live in Volvoland, Hondas in Hondatown. It gave me a new sense of suburban traffic: that it's not about drivers, but simply about cars, all of them roaming ceaselessly in search of a niche.

But at night in the city, drivers are not heading home. They're going out -- to movies, nightclubs, restaurants, baseball games. And so my tails in Boston weren't linear, as they were in the suburbs, but frequently circular -- following cars that were roving about in search of a parking space, like planes wheeling in a holding pattern. In pursuit of one young man in a beat-up Taurus, I tailed him twice around Fenway Park -- glowing with a home game like Emerald City -- before he abruptly did a U-turn by a nightclub and then tried to back into a parking space that was only two-thirds the size of his car. He actually tried to enter the space almost perpendicularly.

Coming from the sleepy suburbs, where you can actually hear the trees rustling at night, everything in the city seems jammed-in, like protons in the atom's core. There's such blasting energy in a place like the Back Bay. On Boylston, by the Pru, the car in front of me was nearly rocking as the driver nodded his head to an electric rhythm, his girlfriend gazing over at him uncertainly, impervious to the beat. I followed them down Comm Ave, swung halfway around the Public Garden, then lost them at the light. But it didn't take a novelist to see how their whole relationship would play out -- the too-cool dude with the ice queen. Good luck.

I spend the night of my Boston tails like a taxi driver, hopping from one "ride" to the next: Brookline to the Fenway to Kenmore Square to Newbury Street to the South End to Beacon Hill. Back and forth, in town and out. I've hoped to cap off the night by tailing a luscious little Miata on Berkeley Street, which, by a quirk, also has a license plate that ends in JB. Such a zippy little car, I'm immediately taken by it, and I like the brunette behind the wheel, too.

I follow her to Storrow Drive, heading in town toward Mass General, but then a huge Lexus cuts in front of me and the Miata zooms free. I think, okay, Mr. Lexus, I'll take you then. It's a big black SUV, one of those cars that take all the gas in the Middle East to fill, and I'm immediately resentful. I stay with him to the traffic lights by the rotary near the I-93 on-ramp. There's a back-up there, and I pull up right beside him, look across to check him out. I once impressed myself by doing a full 360 around a car I was following out the Mass Pike, but this is cool in its way. The guy has a slim, collegiate face with a firm jawline and brush-like hair. I hate him.

I glance around to the other drivers and am astonished by how much I can see: the guy eating a sub to my left, the two middle-aged jerks yukking it up diagonally ahead of me, the hot girl in a tank top behind.

Then the light changes, and we're off. Up the ramp goes Mr. Lexus, then he swerves for the Tobin Bridge. The Tall Ships are in town, and I notice fireworks going off along the South Boston waterfront, great spurts of color arcing high into the night. The Lexus flies ahead across the first, nameless bridge over the Charles, then swings onto the circular ramp that leads to the new tunnel. He is flying. The signs say 35, but he's doing 70, easy. I slam down the accelerator to catch up with the prick. He's weaving in and out of traffic, left lane, right lane. Who is this guy? What's his hurry? We dash across the Tobin, the water smooth below us. I'm four or five cars back, fighting to keep up, when I see a dark SUV up ahead signal a right and then veer off on the Chelsea exit.

My guy didn't seem like the Chelsea type to me, more like North Shore. But there's no time to think. I turn off in hot pursuit -- and see that the SUV I've chased is, in fact, a Massachusetts State Police vehicle. Uh-oh. I slow down abruptly, let that car go on ahead.

I've had my thrills. But I can't quite get the memory of the first JB out of my system, the girl I left in Brookline. I think about those fluttering curtains. I think how I walked along her sidewalk, peered in. I didn't see much, just the pale outline of a couch before a fireplace, with a rattan table beside. I saw that first JB pass through a doorway at the far end of the room, flicking her hair off her shoulders as she went. If I'd only stayed there longer, perhaps I'd have seen something . . . more.

It's only 10 o'clock. I could go back. The Brookline house is on my way home. I could park a block or two down from her door. I could stroll back by her windows, casually, as if I were merely enjoying the night air. If I glanced in through the curtains, I might see her again. I might see her with someone. I might see her alone. She wouldn't know I was there. I could just watch.

Rollins would do this. But, in fiction, I didn't have to worry too much about the recipients of Rollins's gaze. In life, you need to be more considerate. Rollins can circle back if he wishes. As for me, I return to the Tobin Bridge, bound for home. As I pass the turn for Brookline, I say a silent goodbye to the woman of my dreams. And to the man.

John Sedgwick's psychological thriller The Dark House has just been published by HarperCollins.

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