“It’s an alphabetical code,” Hailey said. “These letters all look random—but there’s an order to them, you just can’t see it without a key. Thomas Jefferson and a mathematician consort of his named Robert Patterson worked on something similar—what they called a ‘perfect cipher.’ It’s actually foolishly simple to construct. In Jefferson’s version, you just wrote your message vertically, then broke the text up horizontally, shifted the lines around, and added random letters to each horizontal row. What you were left with looked like—well, this. But all you needed to decipher it was a simple mathematical key that told you where the horizontal lines belonged, and how many random letters were added to each row.”

Nick wasn’t going to pretend he’d followed most of what she’d said; but he understood enough to know that her trick with the battery acid had only been a first step toward understanding whether the eagle and the stolen copper-paged book were more valuable than just antique curiosities.

“You can crack this, right? Use some of that card counting magic of yours?”

“Math isn’t magic, even though sometimes it can seem pretty close. And yes, this sort of code is theoretically crackable. A cryptographer at Princeton did manage to break an example of Jefferson and Patterson’s perfect cipher a few years ago. But it would involve a lot of computing power and more importantly, a lot of time.”

As she spoke, she continued leafing through the book—when she suddenly stopped, her fingers hovering over the final copper page. She looked closer, which made Nick lean in as well. There was an image halfway down the page, etched by the sulfuric acid right into the copper:

Nick stared at the picture a good, long beat. Above the picture were more lines of what seemed like random text—but even so, Hailey was running a finger above one particular line directly above the picture:

leserreursnesontpasdanslartmaischezlartisan

“More gibberish,” Nick said. Hailey shook her head.

“That’s not gibberish like the rest. It’s French.”

She didn’t say more. She was back to staring at the image, seemingly racking her memories.

“It looks almost like some sort of tomb?” Nick tried. “Maybe something Roman or Greek? Or even Egyptian? That strange vase on top—”

Hailey’s eyes lit up. She lurched from the book toward one of the laptop computers on the workbench.

“I need to do a little research—but I think I know what this is.”

A second later, she had the laptop open.

“If I’m right—that image, it’s not from Egypt, Italy, or Greece. It’s something right here in Boston.”

Chapter Eighteen

Chapter Eighteen

You sure about this? From where I’m standing—that doesn’t look anything like the picture in the book.”