He bit his lip. One eyelid ticced. Poor kid was under real pressure. Petra felt bad about ribbing him.

“Hey,” she said, “you’re smart in all kinds of ways. You’ll do what’s best for yourself.”

“I try to tell my mother. My plate’s full enough, I’m not ready for a relationship.”

Petra pointed to the chair alongside her desk. He sat down heavily.

“Lousy date, huh?”

He grinned. “I’m that obvious.”

“Well,” she said, “I figure Mom sets you up with a high I.Q. beauty queen, maybe you’d forget about your plate.”

“The girl was nice enough, but not- We had absolutely nothing in common. Her family’s new in our church. She’s religious and modest, and for my mother, that’s enough.”

“No beauty queen,” said Petra.

“She looks like a mastiff.”

“Ouch.”

“That was cruel,” said Isaac. “But so what? She was also aggressive. Sweet in church but take her to dinner and watch out.” He shook his head.

“Aggressive about what?”

“Everything. She had opinions on matters about which she knew nothing. Religion really got her going. Nuclear-strength dogma. We’d barely sat down and she was telling me I needed to go to church more often. Instructing me what to believe. And not with any particular theological elegance.”

“Oh, boy,” said Petra. “You’re not even married and she’s running your life.”

He laughed again. “You sound like a guy. I mean, that’s something one guy would say to another.” Blushing deeply. “Not that you’re not feminine, you’re very feminine, it’s just that- Are you married?”

“Used to be. It didn’t end because I tried to run his life. I was the most perfect spouse in the universe but he was a lout.”

He said, “You’re joking but I bet that’s true.” He looked at her, helplessly.

“In terms of sounding like a guy,” she said, “I grew up with five brothers. You pick stuff up.”

“That must help in terms of working here- the predominantly male environment.”

Somehow the subject had changed. She said, “It does help.”

He said, “Anyway… about those June 28 cases. I neglected to mention that four of six took place here, in Hollywood Division. I’m not sure yet if it adds another layer of statistical significance to the- ”

“We’re a high-crime district, Isaac.”

“Several divisions have higher homicide rates. Ramparts, Central, Newton- ”

“Maybe you’ve got a point, Isaac. I promise to take a look, but right now I’m kind of tied up.”

“The Paradiso shootings.”

“Exactly.”

“Has that girl been identified?”

“Not yet.”

“Okay. Sorry for- ”

“She had an abortion within the last month or two. That say anything to you?”

“The obvious thing,” he said, “is a possible source of conflict. With the father.”

“Over the abortion?”

“I was thinking of the pregnancy itself. In certain situations, an unwanted pregnancy would be a pretty robust motive for homicide, wouldn’t you say? Theodore Dreiser wrote a wonderful book about it- ”

“She terminated the pregnancy, Isaac.”

“But maybe she kept that fact to herself.”

Petra considered that. Why not? “It’s an angle. Thanks. Now all I have to do is figure out who she is.”

She flashed him a smile and turned back to the mess on her desk.

“Detective Connor…”

“Yes?”

“Would it be feasible for me to ride with you? To observe what you do firsthand? I promise not to be intrusive.”

“It’s pretty boring, Isaac. Lots of routine, lots of dead ends.”

“That’s okay,” he said. “The longer I’m here, the more I realize how ignorant I am. Writing a dissertation about crime and I don’t know the first thing about it.”

“I’m not sure riding along will help you much.”

“I think it will, Detective.”

A trickle of sweat made its way down his left hairline and reached his ear. He swiped at it. How long had he been building up the courage to ask her? Behind the precocious pronouncements was so much anxiety.

“Okay,” she said. “Tomorrow morning, when I recontact some of the witnesses on the Paradiso case, you can come along. But only on one condition.”

“What’s that?”

“Start calling me Petra. If you don’t, I’ll start calling you ‘Dr. Gomez.’ ”

He smiled. “I’m a ways off from earning that.”

“I’ve earned my title but I’m forgoing the honor,” she said. “You’re making me feel old.”

The bus that Isaac took to the Union District was a big, loose-in-the-rivets, half-empty, diesel-fed dinosaur that rumbled and bumped through dark city streets, brakes squeaking, belching pollution. Brightly lit; a crime-reduction measure.

By car, the ride from Hollywood would be twenty minutes. Using the MTA, an easy hour.

He sat at the back, read the latest edition of Davison’s Abnormal Psychology. His fellow riders were mostly cleaning women and restaurant workers, a few drunks. Nearly all Latino, mostly illegal, he figured. Just as his parents had been until the Doctors had intervened.

And now he was wearing his father’s hand-me-down suit and playing at scholar.

There but for the grace…

When he got home, his father would probably be at work. Lately, Papa had been taking a second shift dipping sheets into noxious vats, wanting to earn a little extra money. Isaiah, home from his roofing job, would be sleeping, and Joel, of late a gadabout, might or might not be around.

His mother would be in the kitchen, changed from her uniform to a faded housedress and slippers. A pot of albondigas soup simmering on the stove. A rack of tamales, both savory and sweet, fresh out of the oven.

Isaac had barely eaten all day, taking care to be hungry for her food. He’d learned the hard way his freshman year, eating a late lunch on campus and arriving home with insufficient appetite. Not a word of protest from Mama as she wrapped his uneaten dinner in foil. But those sad looks…

Tonight, he’d gorge as she sat and watched him. Eventually, he’d try to get her to talk about her day. She’d claim it was boring and want to know about the exciting world he lived in. He’d resist, then finally parcel out a few details. Not the crime stuff. The numbers and polysyllables.

A few well-chosen polysyllables always impressed Mama. When he tried to simplify his language, she stopped him, told him she understood.

She didn’t have a clue what he was talking about. In any language multiple regression analysis and percentage of variance accounted for were incomprehensible except to the initiated. But he knew better than to patronize her.

Sensitive guy that he was.

One of the initiated.

Whatever that meant.

He’d dozed off and dreamed when the bus came to a quick stop. Jolted awake, he looked up in time to see the driver throw out a homeless man who’d failed to produce the fare.

Angry words and clenched fists shot through the bus’s wheezing door as the wretchedly filthy evictee stood in the gutter and howled vengeance. Isaac watched the man, bent over in shame, turned tiny by the bus’s departure.

The driver cursed and put on speed.

The cusp of violence. So much of the crime Isaac had studied began that way.

Not the June 28 murders, though. They were something different, he was sure of it. You could lie with numbers, but the numbers he’d divined weren’t lying.

Now to convince Detective Connor.

Petra.

Thinking of her by name was unsettling; it reminded him that she was a woman.

He sat lower in his seat, wanting to sink out of view. Not that any of his co-riders were the least bit interested in him. Some were regulars and surely recognized him, but no one spoke.

The geek in the borrowed suit.

Occasionally someone- a woman not unlike his mother- smiled as he boarded. But for the most part everyone wanted to rest.