R. JERRY HALPERN HAD AN APARTMENT LESS THAN TWO miles from the campus, in a two-story building that had probably been very nice forty years ago. He answered the door right away when Deborah knocked, blinking at us as the sunlight hit his face. He was in his mid-thirties and thin without looking fit, and he hadn’t shaved for a few days. “Yes?” he said, in a querulous tone of voice that would have been just right for an eighty-year-old scholar. He cleared his throat and tried again. “What is it?”

Deborah held up her badge and said, “Can we come in, please?”

Halpern goggled at the badge and seemed to sag a little. “I didn’t—what, what—why come in?” he said.

“We’d like to ask you a few questions,” Deborah said. “About Ariel Goldman.”

Halpern fainted.

I don’t get to see my sister look surprised very often—her control is too good. So it was quite rewarding to see her with her mouth hanging open as Halpern hit the floor. I manufactured a suitable matching expression, and bent over to feel for a pulse.

“His heart is still going,” I said.

“Let’s get him inside,” Deborah said, and I dragged him into the apartment.

The apartment was probably not as small as it looked, but the walls were lined with overflowing bookshelves, a worktable stacked high with papers and more books. In the small remaining space there was a battered, mean-looking two-seater couch and an overstuffed chair with a lamp behind it. I managed to heft Halpern up and onto the couch, which creaked and sank alarmingly under him.

I stood up and nearly bumped into Deborah, who was already hovering and glaring down at Halpern. “You better wait for him to wake up before you intimidate him,” I said.

“This son of a bitch knows something,” she said. “Why else would he flop like that?”

“Poor nutrition?” I said.

“Wake him up,” she said.

I looked at her to see if she was kidding, but of course she was dead serious. “What would you suggest?” I said. “I forgot to bring smelling salts.”

“We can’t just stand around and wait,” she said. And she leaned forward as if she was going to shake him, or maybe punch him in the nose.

Happily for Halpern, however, he chose just that moment to return to consciousness. His eyes fluttered a few times and then stayed open, and as he looked up at us his whole body tensed. “What do you want?” he said.

“Promise not to faint again?” I said. Deborah elbowed me aside.

“Ariel Goldman,” she said.

“Oh God,” Halpern whined. “I knew this would happen.”

“You were right,” I said.

“You have to believe me,” he said, struggling to sit up. “I didn’t do it.”

“All right,” Debs said. “Then who did it?”

“She did it herself,” he said.

Deborah looked at me, perhaps to see if I could tell her why Halpern was so clearly insane. Unfortunately, I could not, so she looked back at him. “She did it herself,” she said, her voice loaded with cop doubt.

“Yes,” he insisted. “She wanted to make it look like I did it, so I would have to give her a good grade.”

“She burned herself,” Deborah said, very deliberately, like she was talking to a three-year-old. “And then she cut off her own head. So you would give her a good grade.”

“I hope you gave her at least a B for all that work,” I said.

Halpern goggled at us, his jaw hanging open and jerking spasmodically, as if it was trying to close but lacked a tendon. “Wha,” he said finally. “What are you talking about?”

“Ariel Goldman,” Debs said. “And her roommate, Jessica Ortega. Burned to death. Heads cut off. What can you tell us about that, Jerry?”

Halpern twitched and didn’t say anything for a long time. “I, I—are they dead?” he finally whispered.

“Jerry,” said Deborah, “their heads were cut off. What do you think?”

I watched with great interest as Halpern’s face slid through a whole variety of expressions portraying different kinds of blankness, and finally, when the nickel dropped, it settled on the unhinged-jaw look again. “You—you think I—you can’t—”

“I’m afraid I can, Jerry,” Deborah said. “Unless you can tell me why I shouldn’t.”

“But that’s—I would never,” he said.

“Somebody did,” I said.

“Yes, but, my God,” he said.

“Jerry,” Deborah said, “what did you think we wanted to ask about?”

“The, the rape,” he said. “When I didn’t rape her.”

Somewhere there’s a world where everything makes sense, but obviously we were not in it. “When you didn’t rape her,” Deborah said.

“Yes, that’s—she wanted me to, ah,” he said.

“She wanted you to rape her?” I said.

“She, she,” he said, and he began to blush. “She offered me, um, sex. For a good grade,” he said, looking at the floor. “And I refused.”

“And that’s when she asked you to rape her?” I said. Deborah hit me with her elbow.

“So you told her no, Jerry?” Deborah said. “A pretty girl like that?”

“That’s when she, um,” he said, “she said she’d get an A one way or the other. And she reached up and ripped her own shirt and then started to scream.” He gulped, but he didn’t look up.

“Go on,” said Deborah.

“And she waved at me,” he said, holding up his hand and waving bye-bye. “And then she ran out into the hall.” He looked up at last. “I’m up for tenure this year,” he said. “If word about something like this got around, my career would be over.”

“I understand,” Debs said very understandingly. “So you killed her to save your career.”

“What? No!” he sputtered. “I didn’t kill her!”

“Then who did, Jerry?” Deborah asked.

“I don’t know!” he said, and he sounded almost petulant, as if we had accused him of taking the last cookie. Deborah just stared at him, and he stared back, flicking his gaze from her to me and back again. “I didn’t!” he insisted.

“I’d like to believe you, Jerry,” Deborah said. “But it’s really not up to me.”

“What do you mean?” he said.

“I’m going to have to ask you to come with me,” she said.

“You’re arresting me?” he said.

“I’m taking you down to the station to answer a few questions, that’s all,” she said reassuringly.

“Oh my God,” he said. “You’re arresting me. That’s—no. No.”

“Let’s do this the easy way, Professor,” Deborah said. “We don’t need the handcuffs, do we?”

He looked at her for a long moment and then suddenly jumped up to his feet and ran for the door. But unfortunately for him and his masterful escape plan, he had to get past me, and Dexter is widely and justly praised for his lightning reflexes. I stuck a foot in the professor’s way, and he went down onto his face and slid headfirst into the door.

“Ow,” he said.

I smiled at Deborah. “I guess you do need the cuffs,” I said.