“Look, Ms. Ethnicographer-”

“Ethnographer.”

He smiled, letting her know he had gotten it wrong as a joke. Or that he didn’t mind being corrected by her. She couldn’t quite read him, and that guarded quality was part of what made him so interesting.

“I’m sure you’re good at what you do,” he said. “But I’m good at what I do, and I’m the person who should be interviewing anyone who has information about this homicide, no matter how tangential.”

“But in your view it’s all straightforward, right? You said you’re sure that Perri brought the gun to school. Maybe this other girl’s information is…apocryphal.”

He didn’t smile at what she thought would be a nice shared moment, their first private joke. “If you keep talking to this girl, she’s going to get rehearsed. Or scared. Or she may actually come to believe whatever version she’s giving you. If you tell me her name, I won’t say how we know about her. I’ll just say we developed it from our investigation.”

“Teenagers aren’t stupid. She’d know it was me. And that’s one thing I won’t do, compromise a student’s faith in me. It’s essential to my work. These girls have to trust me. They’ve been betrayed and bullied, often by those who were once their dearest friends. I teach them how to survive.”

“They give credit for that?”

She knew he was trying to make a joke, but she couldn’t help being a little offended. “Yes. And they should.”

Her sandwich arrived, along with his second beer. He drank off half of it in a few gulps, looked at his watch. “I really should be getting along.”

“Don’t,” she said, then wished she could take it back. “I mean…stay with me. Until I finish my sandwich. I’m a quick eater.”

“Until you finish your sandwich. But don’t get indigestion on my account.”

“I never do.”

In the parking lot, she asked him, “Which way do you go?”

“North. Toward Freeland.”

“Oh, I’m south. Beverly Hills.”

“That’s a nice neighborhood.”

“I’m renovating my own house. I bought this amazing buffet at a yard sale, but then I put a new floor down over the weekend.” She waited to see if he would have anything admiring to say about this. “So it’s ridiculous, but I can’t move it back by myself. My brother says he’ll help me when he visits from New York, but that’s not until later this summer.”

The moment yawned. He looked at her thoughtfully, then took a step backward, jangling his keys. “You drive carefully, now. Someone little as you could be over the legal limit, drinking two beers in an hour.”

But Harold Lenhardt did not drive straight home that night. There was no rush, now that it was clear he would never make Jessica’s meet. He still went north but took a slight detour, stopping at a town house in White Marsh, a place he had visited only once before, for a Christmas party.

Andy Porter-the big blond giant, as Lenhardt thought of him, half amused, half intimidated-opened the door.

“ Nancy know you’re coming?” he asked, clearly surprised. As close as Lenhardt and Nancy were at work, they didn’t socialize much outside the office.

“No, but I was in the neighborhood and thought I should check on her.”

“I’ve fixed her up a place in the sunroom. Less moving around that way. A few steps to the bathroom, a few steps to the fridge.”

The family room was a den on the other side of the kitchen, separated by the now ubiquitous breakfast bar. Hey, there’s another word I know, Lenhardt said to the woman who lingered in his head. “Ubiquitous.”

“Sergeant!” Nancy ’s voice squeaked with surprise. She was lying on a flowery sofa, a thin, summer-weight blanket covering her substantial bulk, the television on mute, a stack of paperbacks within easy reach.

“How you doing?”

“They say okay. It is what it is.”

What it was was toxemia, a potentially fatal condition for mother and unborn child, and Lenhardt was pretty sure that Nancy was scared to death, but there didn’t seem to be any reason to call her on her attitude. If she wanted to play strong for him, he was okay with that. A police should front for the boss.

“I can’t help feeling cheated. I counted on you working until the moment your water broke. I was looking forward to seeing how a pregnant woman functioned in interrogations.”

“You know they would have put me on desk work the moment I started showing.”

“Probably.” Lenhardt was tactful enough not to mention that Nancy, a big-boned girl, could have gone longer than most before that happened. “But you’re okay for now? And the kid’s okay?”

She nodded. “As far as we know.”

“And it’s a boy?”

“It’s a boy.”

“That’s good. Boys are…easier. Maybe because I’m a guy, but our boy seems awfully simple next to our girl.”

“Infante told me what you’re working on-murder in the girls’ room. You feeling kind of blue about teenage girls?”

Lenhardt hadn’t realized he was feeling blue, much less that someone might notice. “I don’t think I understand women of any age. I just talked to this teacher-young, younger than you. Swear to God, Nancy, I think she was coming on to me.”

“Ladies like you, Triple L.” That was Nancy ’s nickname for him, Triple L-Living Legend Lenhardt. “Did she touch your hand?”

“No.”

“Because if a woman touches you in any way-on the hand or arm-she definitely wants to sleep with you. That’s what women do.”

“Where do you learn this stuff? I mean, not just you. Women in general.”

“I could tell you-”

“But then you’d have to kill me, I know.”

“No. But if you knew all our secrets, you’d be even more irresistible, have more women chasing you. That’s not what you want.” A pause. “Right, Sarge? That’s not what you want?”

“I can barely handle the two I have.”

“Two?” She furrowed her brow, worried for him.

“Marcia and Jessica.”

They shared a laugh, but then Nancy started to hiccup, and Andy came in, a bottle of water clutched in his giant hands. Lenhardt let himself out, embarrassed that he had imposed on Nancy at such a time. She had too much on her mind to tend to his conscience.

But he had really wanted to know-not just where women learn such things but what he should do about his own daughter, how he could prepare her for this world without sheltering her from it. He didn’t want to think of his daughter in her twenties all but propositioning a married man old enough to be her father. He didn’t want to think about the man who might say yes.

What Lenhardt didn’t want to know was the truth about himself: If he could have gotten away with it, he would have. Under the right circumstances, if he could have had a fling with a girl like that and be assured he could never, ever get caught, he would have done it in a second. But Infante, with his two broken marriages-and, yes, marriage two was to the woman who broke marriage one-was proof that men did get caught.

And Infante wasn’t the only one who could smell crazy on a woman. There was more than a whiff of it on that teacher-not crazy-crazy, but romantic-crazy, the kind of girl who went in saying she knew the rules, and then, next thing you knew, she was calling your house, indifferent to caller ID. A woman like that claimed to be free and easy, but you paid in the end.

Still, if he could have gotten away with it-if there was some parallel universe where actions had no consequences-he would have. Wouldn’t anyone?

His phone rang, and he almost didn’t grab it. Probably Marcia, busting his balls for not making the swim meet. But he weakened and flipped it open, and the female voice that greeted his was refreshingly businesslike-Holly Varitek, the lab tech.

“Tell me something good,” he said.

“Can’t,” she said. “I’m sorry. I can’t tell you anything definitive. There are at least three sets of fingerprints on the gun, but I’ve only identified two.”