Monday night I was having a cup of coffee in front of the television set when my cell phone rang.

“I feel like a fucking spy,” Louise said. “I’m in the ladies’ room at the restaurant. We’re about to go back to my place. You’ve got the address?”

I said I did.

“This is so deeply weird. I’m going to take him home and have sex with him, and meanwhile you’ll be lurking outside waiting to follow him home. Tell me that’s not weird.”

“If you’d prefer—”

“No, it makes sense, it’s just totally weird. If he’s who he says he is, then he never has to know about this. If he’s not, then I have to know about it.”

I asked if he was likely to stay overnight.

“If he does, it’ll be a first. He usually comes over and stays for three or four hours, but this time we had dinner, which we usually don’t, so we’re getting a late start. What time is it, eight-thirty? No, closer to nine. My guess is he won’t stay past eleven-thirty.”

I asked what he was wearing, to make sure I didn’t follow the wrong guy. Designer jeans and a navy-blue polo shirt, she said. I suggested she could flick the lights on and off a half dozen times as soon as he left the apartment, and she said it was a great idea, but her apartment was in the rear of the building, so I’d never be able to see it from the street.

“But I may just do it anyway,” she said, “because it’s such a cool Mata Hari–type thing to do. Hey, wait a minute. Won’t you have your cell phone with you? So why don’t I just call you when he leaves? And then I’ll flick the lights, too, just for fun.”

Her estimate wasn’t off by much. It was twenty to twelve when my cell phone rang.

“Mata Hari speaking,” she said. “He’s all yours. I have to tell you, dinner was good but the dessert was better. Do me a favor, will you? Call me tomorrow to tell me that he’s David Thompson and he’s single and the only secret he’s keeping from me is that he’s fabulously wealthy.”

I told her I’d see what I could do, and then I rang off and the door opened and he came out. I’d probably have made him without the phone call. He was wearing jeans and a dark polo shirt, and the photo I had of him was a good likeness.

Tailing somebody is complicated enough when you’ve got a full team, half a dozen in cars and about as many on foot. I had TJ along for company, and an off-duty cabby named Leo whom I’d promised fifty bucks for a couple of hours of chauffeur duty.

Louise lived on the third floor of a brownstone on the uptown side of West Eighty-seventh Street between Broadway and West End. Like most odd-numbered streets, Eighty-seventh is one-way westbound. If David Thompson lived in or around Kips Bay, he’d probably take a cab home, and he’d probably walk to Broadway to catch it. The same was true if he wanted to go somewhere else by cab. If he wanted the subway, he’d catch it at Eighty-sixth and Broadway, so once again he’d be walking toward Broadway, and against the flow of traffic.

We’d set up accordingly. TJ and I were standing in the doorway of a building directly opposite Louise’s, while Leo’s car was parked next to a hydrant on Broadway. If a cop rousted him he’d circle the block, but it wasn’t likely, not at that hour. All he had to do was say he was waiting on a fare.

When Thompson left the building, we’d tag him to Broadway, then get in Leo’s car and follow whatever cab he hailed. If he walked down to Eighty-sixth and took the subway, TJ would go down into the tunnel after him. He’d try to stay in touch by cell phone, and we’d try to be there when he and Thompson got off the train.

So Thompson came out the door and down the stoop, looked at his watch, hauled out a cell phone, and made a call. At first no one answered, but then someone did, or voice mail kicked in, because he talked with animation for a moment or two before snapping it shut. He held it out, looked at it, then put it away, got out a cigarette and lit it, blew out a cloud of smoke, and started walking, but not toward Broadway. He headed the other way, toward West End Avenue.

Shit.

“Plan B,” I said, and took off after Thompson, while TJ sprinted to the corner of Broadway and around it to where Leo was waiting with the bulldog edition of the Daily News open on the steering wheel. He had the motor running before TJ was in his seat. New York’s the one place in the country when you can’t make a right turn at a red light, the traffic’s just too chaotic for that to work here, but David Letterman pointed out once that New Yorkers think of traffic laws as guidelines, and Leo figures a grown man ought to be able to use his own judgment. He slid around the corner and picked me up halfway down the block.

I got in back, and Leo coasted to the corner, where the light was red against us. Thompson, when he reached the corner, could have stepped to the curb to flag a southbound taxi, or he might have crossed Eighty-seventh Street himself, or waited for the light and crossed West End and headed for Riverside Drive.

If he’d done any of those things we could have followed him with no trouble, but instead he turned right on West End and headed uptown. Leo might have been willing to push his luck and run another red light, but he’d be going the wrong way on a one-way street, and we couldn’t do that.

“Son of a bitch,” he said with feeling.

“Shoot across to Riverside and come back on Eighty-eighth,” I said, opening the door and getting out again. “I’ll try to stay with him.”

By the time I got going he had a half-block lead on me, which shouldn’t have been a problem, but I lost sight of him when he turned right at Eighty-eighth Street. I increased my pace and got to the corner where he’d turned and he was gone.

Leo, who ran us back to Ninth and Fifty-seventh, wouldn’t take any money. “I thought we was gonna have an adventure,” he said. “ ‘Follow that cab!’ I thought I’d show off my driving skills and tail the bastard through parts of Brooklyn even Pete Hamill’d get lost in. All I did was drive around the fucking block.”

“It’s not your fault I lost him.”

“No, it’s his fault, for turning out to be such an elusive bastard. Put your money back in your pocket, Matt. Call me again sometime, and we’ll have fun, and you can pay me double. But this one’s on the house.”

He’d dropped us in front of the Morning Star, but neither of us felt like going there. We crossed the street to the Parc Vendôme and went upstairs. Elaine was on the couch with a novel Monica had recommended as a perfect guilty pleasure. “She called it the prose equivalent of a three-handkerchief movie,” she said, “and I have to say she was right. What’s the matter?”

“The guy walked around the block and lost us,” I said.

“The nerve of the son of a bitch. You want something?”

“I wouldn’t mind starting the night over,” I said, “but that would be tricky. I don’t want more coffee. I don’t think I want anything. TJ?”

“Maybe a Coke,” he said, and went off to fetch it himself.

I joined him in the kitchen and the two of us tried to make sense out of what had happened to us up in the West Eighties. “It’s like he made us,” he said, “but he didn’t exactly act like it.”

“What I can’t figure out,” I said, “is how he disappeared like that.”

“Magician walks down the street and turns into a drugstore.”

“It was something like that, wasn’t it? He wasn’t that far ahead of me when he turned the corner. Maybe a hundred feet? Not much more than that, and I would have cut the distance some, because I walked faster once the corner building blocked my view of him. And then I got there and he was gone.”

“Even if he turns the corner and starts bookin’, you’d get a look at him soon as you come round the corner yourself.”

“You would think so.”

“ ’Less he ducked into that building.”

“The apartment house on the corner? I thought of that. The street door’s not locked, anybody can get into the vestibule. Then you’d need a key, or for someone to buzz you in. I looked in and didn’t see him, but I didn’t do that right away, not until I’d spent some time trying to spot him on the street. You know, it seemed strange that he would walk to West End instead of Broadway, but if he lived there—”

“Then he just a man going home.”

“A man who lives around the corner from a woman and tells her he lives a couple of miles away in the East Thirties.”

“Maybe he don’t want her coming over every other day to borrow a cup of sugar.”

“More likely a pack of cigarettes. I can see that, actually. You go fishing for a girlfriend online, hoping she doesn’t live in the outer reaches of Brooklyn or Queens, some bus-and-subway combination away from you, and then you find out she’s right around the corner, and you realize there’s such a thing as too close.”

“I don’t know,” he said. “Wouldn’t she recognize him? From seeing him in the neighborhood?”

“You’d think so. New Yorkers may not know our next-door neighbors, but we’re generally able to recognize them by sight. He made a phone call, let’s not forget that part.”

“Right before he lit up a cigarette.”

Elaine had come in to fix herself a cup of tea. “He was phoning his wife,” she said, “to find out if he should pick up a quart of milk on the way home.”

“Or a cup of sugar,” I said. “Or a carton of Marlboros. If he was married, would he get himself a girlfriend around the corner?”

“Not unless he had a well-developed death wish,” she said. “Who was he talking to on the phone, a man or a woman?”

“We couldn’t even hear him,” I said.

“Couldn’t you tell by his body language? Whether it was a man or a woman on the other end of the call?”

“No.”

“TJ?”

“I had to guess, I’d say a woman.”

“You would?” I said. “Why?”

“Dunno.”

“He was just with a woman,” I said, “and from what Louise said he gave a good account of himself. If he wasn’t calling his wife to say he’d had to stay late at the office—”

“And he wouldn’t,” TJ said, “not if he lived five minutes away. He’d just show up.”

“You’re right. So it wasn’t a wife he called.”

“ ’Less it was somebody else’s wife.”

“Jesus,” I said.

“He could have called his wife,” Elaine said. “In Scarsdale, to say he’d be late, or that he wasn’t going to make it home at all. And then he went to the building around the corner.”

“Who’s in the building around the corner?”

“I don’t know,” she said. “You’re the detective.”

“Thanks.”

TJ said, “Could be another woman.”

“In the corner building?”

“Everybody got to be someplace.”

“So he’s two-timing Louise with somebody who lives around the corner from her?”

“Three-timing, if he got that wife in Scarsdale.”

“Maybe she’s a working girl,” Elaine offered.

“Louise? I honestly don’t think—”

“Not Louise. The late date, the woman around the corner. Maybe she’s in the game.”

“But he was just with Louise.”

“So?”

“From what she said—”

“He screwed her brains out?”

“Not the words she used,” I said, “but that was the general impression I got, yeah.”

“Maybe the earth moved for her but not for him. Or maybe he was going for the hat trick. That’s what, hockey?”

I nodded. “When one player scores three goals in a game.”

“I knew it was three goals, I just couldn’t remember if it was hockey or soccer.”

“It’s migrated into other sports, but it’s a hockey term.”

“I wonder where it comes from. Anyway, if he knows a working girl right around the corner from Louise, why not drop over and see her?”

I summoned up the image of him in front of Louise’s brownstone, phone in hand. “He didn’t have to look up her number,” I said. “But he’d have it on his speed dial, wouldn’t he?”

“Probably. That’s what people have nowadays, instead of a little black book.”

“If he was still in the mood,” I said, “why didn’t he just stay upstairs a little longer?”

“Gee, I don’t know,” she said. “Do you suppose it could be that Y chromosome he’s been carrying around all his life?”

“In other words, he’s a guy.”

“When I was working,” she said, “I’d have johns who would get themselves off before they came over, so they could last longer. I had one who was the opposite, he wanted me to keep him right on the edge for like an hour or more and not let him get off at all, so he could go home and give his wife a bounce she wouldn’t forget. That one baffled me, I’ve got to say. I felt like a picador at a bullfight.”

I glanced at TJ to see what he made of her remembrance of things past. If it had any impact on him, it didn’t show on his face. He knew about her career history, he and Monica were about the only people we saw regularly who did, but she rarely talked about it in his presence as she was dong now.

TJ had never known his own mother. She’d died when he was less than a year old, and his grandmother had raised him until her own death. Things she’d told him had led TJ to speculate that his mother had been a working girl, and that he himself might have been a trick baby, an unplanned bonus from an unwitting client. No way to tell, he’d said, and he seemed comfortable enough with not knowing.

But the conversation had lost its way, having essentially abandoned David Thompson for a dissertation on the Men Are Strange theme. I said, “I’m not convinced he went into that building.”

“It might have been another one?”

“Or no building at all. Maybe he knew he was being followed.”

“He wouldn’t,” TJ said, “ ’less he was suspicious to start with. You think he picked up something from Louise?”

“Not if he used a condom,” Elaine said.

“If he’s married,” I said, “he might have suspected his wife was having him followed. That could have made him wary enough to sense us.”

“Way he stood there lighting that cigarette,” TJ said. “Like he wanted a minute to figure out what to do as much as he wanted that nicotine hit.”

“So he turned right instead of left,” I said, “and turned right again at West End, turned against traffic. Then he ducked into a building, or found a doorway or an alleyway to hide in.”

“Why would he do that? To shake the two of you, obviously, but why? Wouldn’t it be suspicious behavior, and wouldn’t you think the last thing he’d want to do if he thinks his wife is having him followed is act suspicious?”

“ ’Less it’s more important that she don’t know where he’s going next.”

I said, “Maybe there was a cab there. Around the corner on Eighty-eighth.”

“He had a cab waiting for him?”

“No, but there could have been one standing there, discharging a fare. And he could have grabbed it and been on his way by the time I turned the corner.”

“Wouldn’t you have seen a cab driving away?”

“If I was looking for it. If it was already halfway down the block, and I was looking around for a man on foot, well, I might not have noticed it. Or he could have had a car parked there.”

“And started it up and pulled out without being seen? Only if you was limpin’ round the corner.”

“He could have parked there,” I said, “and got in and pulled the door shut, but not started up. Because he didn’t want to be spotted.”

“Or because he had something to do first,” Elaine offered, “like make a phone call or look up an address.”

“Or smoke another cigarette,” I said, “or anything at all. There’s too much we don’t know and too many avenues for speculation.”

“Plus all the side streets,” TJ said.

We batted it back and forth a little more, and Elaine said he sounded to her like a man with something to hide, and her guess would be that he was a sex addict. That was a new term, she added, for what used to be just a guy who liked to party, or what earlier generations had called a good-time Charlie, or a gentleman with an eye for the ladies.

That got us talking about how the world didn’t cut you much slack anymore, how yesterday’s pastimes were today’s pathologies. TJ finished his Coke and went home.

“Leo wouldn’t take any money,” I told Elaine, “and neither will I. Tonight’s not going to come out of Louise’s retainer.”

“The $500? Didn’t that get used up a while ago?”

“I’ve barely put a dent in it.”

“You’re a real hard-nosed businessman, aren’t you?”

“The money doesn’t really matter.”

“I know that, baby.”

“I just want to see if I can figure it out,” I said. “It shouldn’t be that hard.”