And for the life of me I couldn't tell you why.

I suppose it must have been automatic. I was going to work, even though I knew my work would be strictly limited to reconnaissance. But a man on his way to work takes the tools of his trade along with him, and that was precisely what I did.

Halfway to the subway station, I realized what I'd done. I thought about going home and putting the tools back where they belonged, and I decided it was a fool's errand. No one was going to put his hand in my pocket, with the possible exception of myself. I wouldn't be doing anything illegal, so no cop would have a reason to frisk me. And it wasn't as if I were walking along with a loaded gun on my hip. They were burglar's tools, that's all. They weren't apt to go off on their own.

Riverdale's a part of the Bronx, but don't be ashamed of yourself if you hadn't known that. They're doing everything they can to keep it a secret. In the classified ads, underHouses for Sale, there's a special section of listings for Riverdale after the Manhattan listings. Then come the Bronx listings, following along after them.

The subway's elevated by the time it gets to the northern reaches of Manhattan, so you can watch through the window as the train crosses the Harlem River and presses on through Kingsbridge and into Riverdale. If you do, you won't spot a billboard that proclaims "RIVERDALE-PART OF THE BRONX AND DAMN PROUD OF IT!" It'd make a nice billboard, but so far no one's been prompted to put one up.

And, when you get off at the last stop at 242nd Street and make your circuitous way south and west on Manhattan College Parkway, so named because it winds its way around the ivied campus of Manhattan College, you might be excused if you leapt to the conclusion that you were in, uh, Manhattan. Manhattan Community College is in Tribeca, and Marymount Manhattan College is on East 71st Street, and you'll find the Manhattan School of Music on Broadway and 122nd. They've got Manhattan in their names, and they're in Manhattan, but Manhattan College, curiously enough, is in Riverdale, and Riverdale is in the Bronx.

Ah, well.The Bronx?/ No, thonx! wrote Ogden Nash, some seventy or eighty years ago. Even then the borough got no respect, and time has not been kind to its image. Riverdale, with its fine old fieldstone houses and its very preppy Riverdale Country Day School, understandably blanches at being mentioned in the same breath as, say, Fort Apache.

I mused on all of this as I tried to find the Mapes house and found myself wishing I'd brought a map along. I have a Hagstrom atlas of the five boroughs at home, and I'd studied the map of Riverdale and plotted my route, but it would have been handy to have the map in front of me now. The atlas says it's pocket-size, but only if you're a kangaroo. I'd thought of tearing out the relevant page, but I'm too much of a bookman to mutilate a useful book on a whim. I have a folding map of Manhattan that I could have taken along, but what good would that do me? Riverdale, despite the likely wishes of its inhabitants, is not to be found thereon. The mapmakers know damn well it's in the Bronx.

There were a couple of convenience stores on Broadway at the foot of the subway terminal, and one of them would probably have been happy to sell me a map of the Bronx, if I promised not to say where I got it. But I didn't even think of that until I'd walked far enough on the winding stretch of Manhattan College Parkway to scramble my mental compass. I was damned if I was going to go back and buy a map and start over, so I kept on going, and took a right on Delafield Avenue and a left on 246th Street, which got me under the Henry Hudson Parkway and within shouting distance of the Hudson River. I kept myself pointed toward the river and hit streets I remembered from the map, and I took a wrong turn here and there but figured it was just part of getting to know the neighborhood, and wasn't that part of my assignment?

And then I was on Devonshire Close, a dead-end street that ran north a single block from another street with the irresistible name of Ploughman's Bush. Riverdale is hilly, and Devonshire Close perched on the slope of a rise, with the houses on the east side of the street-Mapes's was among them-situated at the top of the slope. They were large houses and they stood on good-sized lots, with their lawns angling down to the sidewalk. The lawns looked too steep for easy mowing, and about a third of the homeowners had finessed the problem by substituting a ground cover, ivy or pachysandra, for the usual grass. Mapes had grass, though, and his lawn looked well tended, his shrubbery neatly trimmed. Well, he was a plastic surgeon, wasn't he, given to reshaping things to their aesthetic betterment? He might not be out there with hedge clippers himself, but he'd damn well make sure the job got done.

You couldn't see the Hudson from where I was standing, but when I walked up the driveway to where the house began, there was just a sliver of river visible. You'd see more from the first-floor windows, and you'd have a good view from either of the two higher floors. There's something in the human spirit that longs to look at water, and I think that may explain why so many people have fish tanks in their houses and apartments. It's not the fish, it's the water, and I knew that the folks on Devonshire Close didn't need to stare at tanks full of guppies. They'd be able to see the Hudson.

I returned to the front walk, where all I could see was the baronial manse of Crandall Rountree Mapes, and for the time being that was plenty. It was quite a house, but then so were all the others on the block. A few were of red brick, and two were of Tudor-style half-timbered stucco, but the rest were made of stone, which you'll recall is the very same material they build castles out of. The houses on Devonshire Close weren't castles-I didn't spot a single moat or drawbridge, and not even a portcullis-but there was nevertheless something distinctly castleish-castlesque? castleine? Castilian?-about them. They felt substantial, which was ideal from my point of view, but they also felt impregnable, which was not.No one's getting in here, roared the lion's-head brass knocker in the center of the massive oak door.Go home and start over, murmured the thick stone walls.Don't even think about it, growled the windows, all so neatly outlined at their borders with metallic tape.

The tape indicated the presence of a burglar alarm system, and an extra escutcheon plate just below the Rabson lock on the front door told me the system was a Kilgore. I'm familiar with the Kilgore, and even bought one to increase my familiarity, and for a change familiarity bred not contempt but grudging respect. I couldn't bypass it, not without running an electric drill that would draw more attention than the alarm itself. I could turn it off once I was inside the house, I knew how to do that, but first I had to get in, and the Kilgore system was sitting there smugly and telling me I'd have an easier time getting into Fort Knox.

The thing is, you can get in anywhere. I've never had a look at Fort Knox, and can't see why I would want to-I'm not even certain there's any gold there, are you?-but I'm sure it would be possible to get in. It wouldn't be easy, but you can sail a long ways from Easy before you reach the shores of Impossible.

And the Mapes house wasn't Fort Knox. It might be tricky, but there would be a way in. There always was, and the idea was to spot it now so I'd know just what to do come Friday.

First, though, I walked back to Ploughman's Bush and circled the block. I'd been standing in front of the Mapes house for several minutes, and I didn't want to attract any attention. If anyone had spotted me, I'd give them a chance to watch me walk away, and while I was at it I could get a fuller picture of the overall neighborhood.