She thought Crow was sleeping, but he suddenly turned and placed his hand on her abdomen, her least favorite body part. No matter how strong she got, or how lean, this was always soft and round, untamable. He liked it, though.

“Have you ever been pregnant?” he asked.

“God, no. What a strange question.”

“Not so strange. It happens. Even to people like us, who are careful. Yet in all the time we’ve been together, you’ve never been late by even a day.”

“How do you know? Do you keep track of my cycle?”

“Not exactly. But I’ve just observed that there’s a five-day period each month when you become so unpredictable, so volcanic in your emotions, that it’s a given what will follow. After all, if a woman’s premenstrual, she’s definitely going to be menstrual.”

She bumped him with her shoulder. “I’m not that bad.”

“You’re horrible. Even the dogs have figured it out. I can’t swear to it, but I think Esskay has scratched out a calendar in the backyard, where she crosses off the days.”

“Why are you thinking about this stuff anyway?”

He was behind her, so she couldn’t see his face, but his voice sounded sheepish. “I sometimes think I should be able to tell when you’re ovulating, but I guess that’s just a fantasy.”

“I’d imagine so,” Tess said. “Unless that’s a thermometer between your legs.”

“What?”

“It’s a method of testing fertility.”

“Oh, yeah. I knew that.”

“Of course. You know everything, Mr. Cinco de Mayo.”

They laughed and luxuriated in the pure sensation of a laugh rippling through two naked bodies at once.

But the laugh died so abruptly in Tess’s throat it sounded as if she had inhaled a piece of food and choked on it.

“What?” Crow asked.

“The files. Grab my files.” She didn’t give him a chance to do what she asked; she turned on the reading light next to the bed and found them first.

“I never thought to ask for a catalog of items taken from Tiffani’s house after she was killed. I don’t know if the Frederick cops found anything there, although they must have photographs of the scene. But Carl made a list. He showed me a calendar, one with markings that indicated when Alan Palmer was on the road-or so we thought. Every month, two to three days would be circled. He found it in a drawer and assumed the killer had put it there, to throw him off. Which made sense when we thought an outsider might have killed Lucy. But Alan wouldn’t have bothered to hide it. Not if the calendar was part of his alibi, right?”

“So who put it in the drawer?”

“Lucy. She was keeping track of her cycle, trying to figure out when she was fertile. Which is old-fashioned and incredibly unreliable, but some people might still do it that way.”

Tess had found the place in the file where Carl had inventoried the things he took from the rental house. Yes, there was the calendar, with a description of the markings that appeared over the last three months of Lucy Fancher’s life. They had assumed these notations showed Alan’s travel days, when he had chosen the time of Lucy’s death.

But Lucy’s body had, in effect, chosen those days. From the moment she began keeping this record, probably at her beloved’s request, Lucy had begun her own countdown to the day she would die.

“Women do that?” Carl asked, blushing redder than Tess had ever seen him.

“Some do, I guess. It’s not mandatory. They don’t hand you a calendar when you turn thirteen and say, ”Hey, get cracking.“ ”

“Jesus, Tess.” Carl dropped his head so low in embarrassment that his nose was almost touching the place mat at the Suburban House. Tess had convinced him to leave the barracks for lunch a second time in a week, a great triumph. Getting him to this Jewish deli was an even bigger coup. Carl seemed mildly alarmed by everything here, from the mock-tough waitresses to the Yiddish witticisms on the paper place mats. And he hadn’t even seen the pots of schmaltz.

“Actually, from what I know of friends who have been seized by the desire to reproduce, it’s not a very good method. I’m surprised they were using it. I’m surprised they were using anything.”

Carl lifted his head warily. “What do you mean?”

“This was a pretty newly minted relationship.”

“So? Not everyone waits ten thousand years to have a baby.”

Was he making some veiled reference to her and Crow? Tess let it pass. “Yes, but even if they had decided to conceive a child, they wouldn’t have needed a calendar.”

“I don’t follow you.”

“Carl, I’m trying to be respectful of your apparent delicacy when it comes to such matters, but when you’re young and allegedly in love, you don’t need to keep a calendar of the best time to try to conceive a child.”

“Why not?”

Tess’s voice was louder than she intended. “Because, Jesus Christ, Carl, when you’re in a new relationship you have sex all the time.”

That got everyone’s attention, especially the waitress who was standing over them, waiting to take their order.

“Y’all want anything?” asked the woman, a tall, solidly built black woman. “I mean, from the menu.”

Carl meekly ordered a roast beef sandwich, adding a bowl of matzoh-ball soup when Tess promised him it was really just chicken soup with a bonus. She asked for the kreplach and kishkas with gravy.

“I don’t think you can make generalizations about people’s sex lives,” Carl said, barreling through the sentence as if he just wanted the topic to go away. “And in the case of a serial killer, you have to recognize that he derives a great deal of sexual satisfaction from his crimes. The man we’re looking for may not be able to function normally. He may not be able to function at all.”

“Did you ask any of Lucy’s friends about her sex life?”

Carl’s face was now redder than his hair.

“Not straight on, the way you would. But I gave them open-ended opportunities to discuss the relationship. You know the rest-everyone said he was perfect. She never confided the least bit of doubt about him, except to wonder how she had gotten so lucky.”

“Look-your theories and mine don’t necessarily contradict one another. Lucy was keeping a record of her fertile days. Let’s say that our killer does have a difficult time”-Tess tried to think of an expression that wouldn’t make Carl dive under the table from sheer embarrassment-“meeting expectations in this one sphere of the relationship. Maybe he turns this into a strength. He could tell the women-I don’t know, that he doesn’t want to have sex just to have sex, he wants to make a baby with them.”

“Or that he’s born again,” Carl said, “and he wants them to wait until they get married. I knew a guy like that at headquarters.”

Tess nodded. It took time, but she and Carl eventually got in sync. “Think how romantic that would seem to young women like Tiffani and Lucy. Young as they were, they probably had their fill of bad, indifferent sex. Maybe he even chose”-she groped again for another delicate turn of phrase-“to please them in alternative ways.”

“Alternative-oh, you mean-?” Carl looked around the restaurant, as if convinced that the tables of elderly customers were hanging on their every word. But most were simply scooping up chicken fat and diving into belly lox without a care in the world.

“Right. What if-bear with me here-what if he is a she?”

“How can that be?”

“Ever read Yentl the Yeshiva Boy?” As Carl’s roast beef sandwich on whole wheat with mayo arrived, Tess realized he didn’t have even a passing familiarity with Isaac Bashevis Singer. Besides, film was Carl’s preferred reference point. “Or that movie Boys Don’t Cry, about the teenage girl who pretended to be a boy?”

Carl shook his head. “Not my kind of movie. But I saw the documentary, which came first. Besides, she was found out. She didn’t keep her secret for long.”

“Okay, but what about the real-life case of Billy Tipton? He passed as a man through five marriages. No one knew he was born Dorothy Tipton until the day he died.”