A moment later, they were walking back on Newbury, headed toward the rental. It was dark, cold, and misty, but the street was well lit, which mitigated the gloominess.

“Do you want to pick up some coffee before we head back?” Decker asked.

“Sure. Let’s go to Dunkin’ Donuts. I’ve developed a taste for cronuts.”

Decker got into the driver’s seat, turned on the motor, and warmed up the engine. “Want to tell me what the Latin meant?”

“Sure. Fortes fortuna adiuvat means ‘fortune favors the bold.’ Fortis in arduis literally means ‘strong in difficulties’: sort of what doesn’t kill us makes us stronger. He used the phrase Mala fide means—”

“In bad faith.” When McAdams looked at him, Decker said, “Not hard to figure out. Also law school.”

“Right.” McAdams rubbed his hands together.

Decker said, “Who do you know at Harvard who does codes?”

“A professor I had. Brilliant guy. Codes are his hobby.”

“Hold on.” On speakerphone, Decker called Mulrooney and asked the Summer Village detective if it was all right to show the notebook to a third party at Harvard.

“I could probably find someone at Tufts,” Mulrooney said.

“Latham worked at Tufts,” Decker said. “I’d rather use another university.”

“That makes sense,” Mulrooney said. “What’s that guy’s name?”

“Dr. Mordechai Gold,” Tyler told him. “He’s a tenured professor in the math department. I took his class on game theory. I doubt that he’ll remember me, but he’s brilliant and I know he’s an expert at code cracking. He’s probably not going to be able to help us right away, but at least we can drop off the notebook.”

Mulrooney said, “Yeah, you can call him up. Let me know what he says. Keep me in the loop, guys.”

“As soon as we have a clue, we’ll pass it on.” Decker hung up his cell.

McAdams was on his phone. “Okay, I’ve got a department number.” He punched in the numbers. “Do you want to talk to him or should I?”

“You do it.”

“Right.” McAdams pressed the green button. After being put on hold, he was finally connected to Professor Gold’s office. “It’s a machine.” He waited. “Hello, Professor Gold, this is Detective Tyler McAdams from Greenbury Police Department in upstate New York. I took your game theory class four years ago and I remember your expertise in code cracking. My partner, Detective Peter Decker, and I are working a puzzling case and could use some advice. If you could call me, I’d appreciate it.” Tyler left his cell number, Decker’s cell number, and then he hung up.

“Perfect,” Decker said. “You didn’t tell him anything specific but you piqued his interest. You’re turning pro, McAdams. I now have a partner instead of dead weight.”

“You have a way with words, Decker.”