Chapter Five #3
And no clarity with which to think.
The situation with Mr. Finch was too incongruous to be normal. But between Lady Ingram’s anguish, Mrs. Watson’s distress, and her own discomfort with having Lady Ingram as a client, Charlotte couldn’t pin down exactly what was bothering her.
It was as if she were trying to listen to someone timidly tapping out a message in Morse code on the window, in the midst of a hailstorm.
She pushed away from the door. The dossier from Lord Bancroft lay on her bed. She pulled out the next envelope.
A cipher: a page of uppercase letters with no breaks.
The clue informed her that it was a Vigenère cipher.
Vigenère ciphers had been in use for centuries but were first solved only a generation ago.
Mr. Charles Babbage, who managed the groundbreaking feat, did not publish his methods.
But Charlotte, with a mind in search of use and a great deal of time, had made Livia compose several Vigenère ciphers, so she could learn how to decode them on her own.
And what she learned was that solving Vigenère ciphers was an experience best compared to being kicked in the head by a distempered mule. Repeatedly—because not only was it brain-crackingly difficult, but the long, drawn-out process could not be made shorter or less tedious.
Lord Bancroft believed this to be the kind of mental exertion that would give her pleasure?
To be fair, before she knew exactly what solving Vigenère ciphers entailed, she had thought so, too.
At least now she knew that Lord Bancroft had instructed his underling to select difficult cases for her—and that most certainly counted as a point in his favor.
A Caesar cipher, despite its majestic name, was a simple one, in which each letter of the plaintext was replaced by another letter a fixed number of positions up or down the alphabet. In a Caesar cipher with a right shift of 2, for example, A was replaced by C, B by D, and so on.
The Vigenère cipher incorporated the principle of Caesar ciphers. First, Charlotte constructed a tabula recta, a twenty-six-by-twenty-six square that represented all possible letter-to-letter substitution schemes.
If she were writing the cipher, this would be the point at which she chose a keyword.
To encode the sentence CHARLOTTE IS SHERLOCK, with the keyword HOLMES, she would write the following:
CHARLOTTEISSHERLOCK
HOLMESHOLMESHOLMESH
In coding the first letter C, one consulted column C, row H of the tabula recta. The next letter was to be found at the intersection of column H, row O. The process was repeated as many times as there were letters in the original message. In the end, the cipher text would read:
JVLDPGAHPUWKOSCXSUR
But since someone else had chosen the keyword for this cipher, Charlotte must first find out what it was.
She examined the huddle of letters that formed the cipher text, looked for repeated sequences, and counted the number of letters between each iteration of the same sequence—to help determine the length of the keyword.
By the stroke of midnight, her temples throbbed. Mr. Babbage, in fact, had turned down the opportunity to decipher King Charles I’s coded letters—probably because his head still ached from the Vigenère ciphers.
She rose and walked to the window. Almost immediately she saw Lord Ingram in her mind’s eye.
Winter, two months after his wedding, at a house party in the country.
She had come upon him outside, on a snow- and mistletoe-draped terrace.
He had been smoking, his head tilted back, blowing a leisurely stream of smoke into the air.
His eyes had been closed—and he had smiled at the overcast sky. At what he believed to be a benevolent universe.
“Hullo, Holmes,” he said, his shoulders relaxed, his eyes still closed, and a trace of smile still on his lips. “Aren’t you going to ask me how I knew it was you?”
“You’d tell me because no one else would stand here without saying anything.”
He laughed and opened his eyes. “It’s you all right, Holmes.” He took a drag on the cigarette. “You look different. Have you lost weight?”
She had. “No,” she said. “You look happy. Marriage must agree with you.”
“It does indeed.” He was magnanimous in his happiness, refraining from reminding her that she had warned him against this particular match. “You should give it a try.”
He and his wife had come back only a few days ago from their honeymoon, their return more than a fortnight late. They had arrived at the house party in the afternoon but had not made an appearance at dinner. Lady Ingram was said to be a little under the weather.
Charlotte felt as if she had been harpooned. “You’re going to be a father, aren’t you?”
Present-day Charlotte turned away from the window.
It was the most joyous she had ever seen him. She’d never trusted that joy, but to look back, knowing exactly how false its foundation had been, how ephemeral its soap-bubble brightness . . .
She marched back to the desk and reimmersed herself, almost gratefully, in the mind-pulverizing tedium of the Vigenère cipher.