“I told you we came to the right person,” said Patton. Ruthie felt herself blush as she finished setting up the wiring and began flicking a series of switches on the side of the machine. Usually she programmed the machine for groups of tourists and schoolchildren, always deciphering the same sample message. But after closing time, she often worked on actual Enigma messages in the Bletchley archives, thousands of which had never been decrypted. She loved the challenge of decrypting a seventy-five-year-old message, even though it was of no importance whatsoever and could be decrypted by modern computers in a matter of seconds. But this message, apparently, was important. And not only was she decrypting an important message that had never been deciphered, she was doing it for Patton Harcourt. Patton who stood next to her and whose presence raised the same goosebumps on her arms that it had fifteen years ago—even with the metallic, oily odor of the Bombe filling the room.

“Now, we set the drums to the relative position of the first three letters of our crib,” said Ruthie. She began to spin around the red, green, and yellow drums on the front of the machine, relishing Nemo’s complete bewilderment. Patton’s expression was one Ruthie remembered from class—that contracted face Patton made when trying hard to solve a problem. Ruthie knew Patton’s confusion meant that she hadn’t paid attention to the professor all those years ago, had instead focused her attention on the British girl at the next desk.

“There,” said Ruthie, when she had finished setting up the machine. “Now we power up and begin the run. The three rotors in the Enigma machine each have twenty-six possible settings, one for each letter. That means a total of seventeen thousand five hundred seventy-six possible rotor configurations. The Bombe can get through all of those configurations in less than fifteen minutes. Any time a setting seems to match our menu it stops, and we record the setting and test it against our crib. Usually you get four or five stops in a run, but only one of them will be right. Once we find the right one, we’ll have the rotor configuration and one of the connections on the plugboard. The rest is easy.”

“Easy for you,” said Patton, laying a hand on Ruthie’s shoulder.

“Are you ready?” said Ruthie.

Patton did not answer but squeezed Ruthie’s shoulder. She felt a shiver run through Ruthie’s body, and then the room filled with noise as Ruthie turned the machine on and the Bombe began its work.