“Rudy Nasser,” Buckman said. “Brilliant young man. He has advanced degrees in physics and mathematics from USC. He could have a very good position at any top school in the country. He came up here to work with Dr. Zahn. He’s probably one of a handful of people in the world who can truly follow the density of Zahn’s reasoning. He probably understands the man better than anyone. You’ll want to talk to him.”

“Marissa Fordham is dead?”

Mendez went instantly on guard. All he had said was that Dr. Zahn’s neighbor had been killed.

“It has to be Marissa,” Nasser explained. “She’s the only neighbor Dr. Zahn ever visits.”

Rudy Nasser sat back against the edge of the desk. The lecture hall had emptied out except for a couple of students still copying notes from the big chalkboard. It looked like Aramaic to Vince. The students—both cute girls—seemed more interested in stealing glances at their teacher than his mathematical concepts.

“Did you know her?” Mendez asked.

Nasser pulled in a deep breath and blew it back out as he processed the information and whatever it meant to him.

“This is bad, man.”

In his mid-twenties, he looked like a beatnik with the black goatee and soulful dark eyes, and dressed like a Miami Vice drug lord in a slouchy charcoal suit over a black T-shirt and loafers with no socks. He was undoubtedly as socially smooth as his mentor was socially awkward.

“Yes, I knew her,” he said. “Dr. Zahn ...”

He shook his head and left the thought unfinished.

“Dr. Zahn what?”

Nasser shrugged, not wanting to say too much. “Was fond of her. He found her body?”

“Yes,” Vince said. “He called nine-one-one.”

“He didn’t tell me. When he called this morning I knew something had happened. He was so agitated. But he wouldn’t tell me.”

Vince could see him planning damage control, how to get his eccentric boss away from the fray of a murder investigation.

“How well did you know her?” Mendez asked.

“Well enough to have a conversation. I gave her my number to call if she needed me.”

“Needed you to what?”

“To come get Dr. Zahn. He doesn’t always know when he’s worn out his welcome. When he gets manic he loses all sense of time.”

“Does that happen often?” Vince asked, trying to imagine Zahn in a manic state. He had seemed closer to catatonic that morning.

“Not often.”

“Recently?”

“A couple of weeks ago.”

“How is he during these episodes?” Vince asked.

“Happy,” Nasser said. “Euphoric, in fact. Like he’s in the throes of some kind of rapture. He becomes animated, can’t stop talking about whatever idea has taken hold of him. He’s done some of his best work in that state of mind.”

“How did Ms. Fordham react when this happened?” Mendez asked. “Was she afraid?”