He led the way to the exhibition area and stopped in front of a display case that held a brown wooden cylinder mounted on a spindle. The cylinder was about two inches in diameter and eight inches long and was constructed of a series of disks. The rims of the disks were inscribed with letters.

“This was found in a house near Monticello,” Harris said. “We believe it’s a ‘wheel cipher’ Jefferson invented when he was serving as Washington’s secretary of state. You write your message and rotate the disks to scramble the letters. The person getting the message un-scrambles them with a similar device.”

“Looks like something out of The Da Vinci Code.”

Harris chuckled. “Ol’ Leonardo would have been fascinated by the next evolution of the wheel cipher.”

He dragged her over to another display case containing several machines that looked like big typewriters.

She read the placard. “Enigma cipher machines,” she said with excitement in her eyes. “I’ve heard of them.”

“They were one of the best-kept secrets of World War Two. People would have killed for one of these contraptions. They were basically glorified versions of Jefferson’s wheel cipher. He was far ahead of his day.”

“Too bad we can’t use one of these things to decipher his writing,” Angela said.

“We may not have to,” Harris said.

They returned to Harris’s office, where he plopped behind the desk again. He leaned back in his chair and tented his fingers.

“How did you get into codes and ciphers?” he said.

“I’m good at math. I do the crosswords, and I’ve liked acrostics since I was a kid. My interest in puzzles got me into reading books on the subject. That’s where I read about cipher grilles and Jefferson’s interest in cryptology.”

“Half the cryptologists in the world would have given me the same answer,” Harris said. “It was exactly those interests that allowed you to sense the possibility of a hidden message in this stuff.”

She shrugged. “Something about it struck me as being funny.”

“‘Funny stuff’ is what the NSA deals with on a regular basis. Jefferson would have felt right at home in the agency.”

“Where does his wheel cipher fit it?”

“It doesn’t. Jefferson got away from cipher devices later in his career. My guess is that he only used the grille to create a steganograph to conceal the fact that the artichoke info contains a secret message. He would have jotted down the message in the apertures and built sentences around them.”

“I noticed that the syntax in the text seemed stilted or just plain weird in some of the lines.”

“Good catch. Let’s assume Jefferson used this as an extra layer of concealment. First, we’ll have to copy the letters exposed by the holes in the grille.”

Angela pulled a notebook out of her briefcase and handed it over. “I’ve already done that.”