"Yes," said Kennedy in a low tone, "the checkerboard. It took me some time to figure it out. It is a cipher that would have baffled Poe. In fact, there is no means of deciphering it unless you chance to know its secret. I happened to have heard of it a long time ago abroad, yet my recollection was vague, and I had to reconstruct it with much difficulty. It took me all night to do it. It is a cipher, however, that is well known among the official classes of Russia.
"Fortunately I remember the crucial point, without which I should still be puzzling over it. It is that a perfectly innocent message, on its face, may be used to carry a secret, hidden message. The letters which compose the words, instead of being written continuously along, as we ordinarily write, have, as you will observe if you look twice, breaks, here and there. These breaks in the letters stand for numbers.
"Thus the first words are 'Many thanks.' The first break is at the end of the letter 'n,' between it and the 'y.' There are three letters before this break. That stands for the number 3.
"When you come to the end of a word, if the stroke is down at the end of the last letter, that means no break; if it is up, it means a break. The stroke at the end of the 'y' is plainly down. Therefore there is no break until after the 't.' That gives us the number 2. So we get 1 next, and again 1, and still again 1; then 5; then 5; then 1; and so on.
"Now, take these numbers in pairs, thus 3 - 2; 1 - 1; 1 - 5; 5 - 1.
By consulting this table you can arrive at the hidden message.
He held up a cardboard bearing the following arrangement of the letters of the alphabet: _____________________________________ |_________1_____2_____3_____4_____5___| |___1_____A_____B_____C_____D_____E___| |___2_____F_____G_____H_____IJ____K___| |___3_____L_____M_____N_____O_____P___| |___4_____Q_____R_____S_____T_____U___| |___5_____V_____W_____X_____Y_____Z___|
"Thus," he continued, "3 - 2 means the third column and second line. That is 'H.' Then 1 - 1 is 'A'; 1 - 5 is 'V'; 5 - 1 is 'E' - and we get the word 'Have.'"
Not a soul stirred as Kennedy unfolded the cipher. What was the terrible secret in that scientific essay I had puzzled so unsuccessfully over, the night before?
"Even this can be complicated by choosing a series of fixed numbers to be added to the real numbers over and over again, Or the order of the alphabet can be changed. However, we have the straight cipher only to deal with here."
"And what for Heaven's sake does it reveal?" asked Saratovsky, leaning forward, forgetful of the fever that was consuming him.