Page 30 of Absent Reason

"I was hoping to talk to anyone who might have known Victoria Crossing."

The professors exchanged glances, looking at each other before the younger one nodded. "I knew Victoria," he said. "We weren't particularly close, but we taught in the same field. What can I help you with?"

"I'm trying to find out if there was anything unusual about her behavior over the last few days or if she mentioned anything to you that could help us understand why someone would want to harm her," Amber said.

The professor frowned, shaking his head after a few seconds. "No, I can't say that I noticed anything out of the ordinary."

"Has she had any conflicts with any of her colleagues, or problems with her students, in the last few weeks?" It seemed like another important avenue to check up on.

The young professor shook his head. "That's not something I would really know about, but certainly I haven't heard of anything like that."

Amber had been hoping for more, for something that would point her at more potential suspects. She continued to make her way through the department, heading for an administration office, hoping that she would be able to get a full list of staff and students there. If necessary, she would go through each name in turn using the FBI's systems, checking for any prior convictions or red flags that might point to someone capable of this kind of violence.

Even as she walked, though, Amber found herself thinking about what the small group of professors had been doing. Mathematical modeling of patterns was common enough, seeking to understand behavior in the real world with often simple mathematical rules.

Amber wondered if this killer was doing the reverse. Was there a chance that he'd set himself the challenge of killing according to some specific pattern that was more complex than the ones she’d been looking at before?

Amber started to pull up a map of the city on her phone but then spotted a much larger, poster-sized map of it displayed on one of the walls of the math department. It clearly showed the city clinging to both sides of the river, the two islands in the middle, and the seven bridges connecting its various sections.

As she looked at it, Amber started to plot out where the murders had taken place, looking for some kind of pattern. Of course, with only three data points, it wasn't possible to get much of a sense of what was going on. They formed a rough triangle, but so would any three murders spread out across a town like this. There didn't seem to be anything to let Amber know where the killer was based or where he planned to strike next.

There was still that lingering feeling that some fact about the city wanted to spring into Amber's mind. It was like an itch somewhere deep in her brain. It was something about the layout of it, something familiar. Something thatwasn'tabout Verdice but was about another city with almost the same layout.

Amber got out her phone, checking her guess. As soon as she found what she was looking for, she knew that she was right. She felt her heart beating faster as she realized that she might be onto something. She called Simon, wanting to tell him what she'd found, wanting to make this real rather than just a theory.

He picked it up after only a couple of rings.

"Bad news, Amber," he said as he answered, his tone conveying his disappointment. "I'm pretty sure Professor Samuels' alibi is solid. His student's roommate remembers seeing him arrive."

"The Konigsberg Bridge Problem!" Amber said, unable to contain her excitement at what she'd found even long enough to lead into it properly.

"What?" Simon said, now sounding puzzled.

"It's a mathematical puzzle about the bridges of the old city of Konigsberg, what’s now Kaliningrad. The city had seven bridges, and the challenge was to walk over them all without retracing your steps. It was impossible to do, but it got me thinking about our case. Verdict has a very similar layout to Konigsberg, with two central islands and seven bridges. If we want to know what links together a math department and the bridges in this city, it's that."

"That's a stretch," Simon said skeptically. "Especially when Victoria Cressing wasn't killed on a bridge."

"Maybe that's because we guarded the bridges, or maybe there's something else," Amber said. "I want to go back to her apartment."

"What for?" Simon asked. "The forensic team already said that they didn't find anything there."

"I'm not looking for forensic evidence," Amber said. "I'm looking for anything connected to the bridge problem. If there's anything there, anything at all, it will prove that I'm right, and it will give us the link that we’re looking for in this case."

If Amber was right, it would mean that there was a killer out there obsessed with an impossible mathematical problem, one who was prepared to murder people over it. That knowledge might finally help them to understand what was happening here, and it might let them know what the killer was planning to do next.

CHAPTER EIGHTEEN

Amber didn't wait for Simon when she reached the apartment building but headed straight for the entrance, determined to find anything that connected Victoria Cressing to the bridge problem.

There weren't as many reporters outside the apartment building now; they clearly thought that they'd gotten as much of the story there as they were going to get, so most of them had drifted away. So had the forensic teams and the coroner's people. There was just a single police car out front, presumably to keep away anyone who wanted to look around.

"Agent Young, are you making any progress on the case?" one of the few remaining reporters there called out as Amber approached.

"No comment," Amber called back. She didn't want to give away anything to the press in case it got back to the killer. She didn't want to turn this into some kind of contest between him and the FBI. That risked escalating the situation dangerously.

Besides, she didn’t want to admit how little progress she and Simon had made so far. It felt too much like an admission of defeat.

Amber flashed her badge to the officer outside, who stepped aside to let her in. She took the stairs up to Victoria's apartment and let herself in past the police tape, taking a deep breath as she looked around the room.

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