"I use… well, the same number for everything."

"And it's probably either your birthday or the last four digits of your Social Security number."

It was one or the other, from her reaction, but at least she didn't tell me which one. "It's my AOL password, too. I guess I'd better change it."

"As far as your aunt and uncle's alarm system was concerned," I said, "anybody could have let that slip. A burglar is as good as his research, and the smart ones learn to use people who don't even know they're being used. Repairmen, delivery boys. Maybe they had someone doing work in their house, building bookshelves or rewiring the top floor, and he needed to be able to get in and out in their absence. They knew they could trust him."

"And he never told anybody," T J said, picking it up smoothly. "Only he mentioned to his wife that these people were so sentimental they used their wedding anniversary to get in and out of their house. And she told her son, so he'd know that it wouldn't be a good idea to forget his parents' wedding anniversary, and then the kid got into drugs and wound up on Rikers Island, and somebody brought up the subject of burglar alarms, and he knew these people who used their wedding anniversary as a password. If the right person heard it, all he'd need to do was find out when those people got married, and how hard would it be to get that information?"

"Or Kristin could have let it slip," I said. " 'My parents are so sentimental…' and if the right person's listening…"

She nodded, taking it all in, then frowned. "They got in the front door," she said. "They must have had a key."

"Do we know they used the front door?"

"They would have had to, wouldn't they, to turn off the alarm in time?"

"They'd have forty-five seconds or a minute, depending on the system. That's enough time if you know what you're looking for. But you're probably right, they probably went in the front door. That doesn't mean they had a key."

"Wouldn't it show if they broke in? And wouldn't my aunt and uncle have seen the door was forced, and not gone in?"

"Same answer to both questions," I said. "Maybe and maybe not. A skilled burglar can pick a standard pin-and-tumbler lock without leaving obvious signs. It takes a few minutes, it's not as easy as they make it look in the movies, but you don't have to be Houdini. If you're not up to picking a lock, there are any number of ways to force a door without leaving it in splinters. Would there be any signs of forced entry? Probably, but you might need good light and a magnifying glass to spot them. Returning to your own house after a brief absence, with no reason to think anyone might have paid you a visit, you might not look too closely."

We went over it some more, and she kept nodding and fussing with her hair and emitting soundless whistles. "I was just making something out of nothing," she said. "I should have called you and told you not to come. I dragged you up here for nothing."

T J pointed out that it wasn't as though we'd flown in from London. "Rode up on the One train," he said. "Not a big deal."

And I told her it wasn't for nothing. "You had suspicions, and they weren't entirely groundless. There were questions in your mind that you couldn't put answers to. How do you feel now?"

"A little foolish, I guess."

"Besides that."

She thought about it, then nodded slowly. "Better," she said. "Kristin's all I've got left of my aunt and uncle, and at the funeral I couldn't look at her without thinking, well, uncomfortable thoughts. I just hope she didn't get any sense of what was going through my mind."

"She probably had other things to think about."

"Yes, of course."

We talked some more, and she and T J said something about someone with a French name, probably from the course they were taking. Then she reached for the check, but I already had it. She protested that the least she could do was pay for our meal. Or, failing that, for her own.

"Next time," I said.

We were at 122nd and Broadway, and the IRT stops at 116th, then comes up from underground and stops again at 125th. We were three blocks closer to the elevated platform at 125th Street, but it goes against the grain to walk opposite from the direction you're headed. I don't know why it should, you wind up catching the same train either way, and if it had been pouring I suppose we'd have worked it out logically and walked uptown to catch our downtown train. But it was a nice enough day, cooler and drier than it had been, and we felt like walking. At 116th Street we looked at each other, shrugged, and kept going.

Someone made a TV documentary a few years ago about a walk the whole length of Broadway, from the foot of Manhattan to the island's northern tip. Or maybe they didn't stop there, because Broadway doesn't. There's a bridge over the Harlem River and the street keeps going on the northern side, through Marble Hill (which is technically part of Manhattan, although there are people living there who think they're in the Bronx). If the TV people went that far, they probably pushed on through Kingsbridge and Riverdale to the Westchester County line, but if they'd wanted to they could have stayed on Broadway clear to Albany.

It's a great street, following an old road and thus cutting across the rectilinear grid of Manhattan. It had been a long time since I'd walked this stretch of it, and I was enjoying it.

Aside from reaching for the check at coffee shops, walking's about the only exercise I get. Elaine goes to the gym three mornings a week and takes a yoga class a couple of times a month, and every other New Year's I resolve to do something similar, and invariably give it up, whatever it is, before January's out. But they say walking's the best exercise of all, and I hope they're right, because it's all I've got.

Uptown-downtown blocks run twenty to a mile, so we'd covered something like a mile and a quarter when we got to Ninety-sixth Street. "Case you getting sick of this," T J said, "this here's an express stop."

"We need a local anyway," I said.

"How you figure?"

"Columbus Circle's not an express stop," I said. "On the D or the A, yes, but not on the IRT."

"Seventy-second's an express stop," he said.

"Seventy-second?"

"Ain't that where we goin'?"

"Seventy-fourth, you're thinking about."

"So?"

"No real point in going there."

"So you want to catch the local and go on home?"

We had walked a block past Ninety-fifth while we were having this conversation. No harm, there's another entrance at Ninety-fourth, and it saves you an extra two flights of stairs, one down and one up.

I said, "Ninety-fourth to Seventy-fourth, that's what, twenty blocks?"

"I could work that out, but I do believe I left my calculator in my other pants."

"We walked this far," I said. "We could walk the rest of the way, if you're up to it."

"If I up to it," he said, and rolled his eyes.