His sister, Miss Varney of Muswell Hill, hurried to Baker Street and recited a tearful story to Sherlock Holmes, while her brother in his cell awaited a summons from the firing-squad. Holmes at once secured the intervention of the Foreign Office in London and the Mexican Ambassador was summoned. In Mexico City, the British Minister confronted President Carranza himself. Between them, Mr Balfour and his Minister persuaded the Mexican authorities that Mr Varney was unlikely to be the originator of a plot to forge notes that were worth only a few English pennies. Within two days he was released.
Mr Varney had vowed to do anything for Holmes in return. Several months ago, he had redeemed this pledge by infiltrating the office of Posts and Telegraphs in Mexico City. Under revolutionary law, coded telegrams were forbidden for fear that they might be used to start yet another revolution. However, the government minister responsible frequently permitted commercial codes to escape scrutiny, in exchange for a small bribe. Mr Varney, in his turn, had been able to bribe a lesser functionary. This man would alert him to the texts of incoming Western Union telegrams from Count Bernstorff in Washington to Minister Eckhardt at the German Mission in Mexico City.
“It is simple enough,” said Holmes, next morning at the breakfast table. “The United States Embassy in Berlin may forward German telegrams to the State Department in Washington -and so to the German Embassy. However, the State Department will not forward them to the German Minister in Mexico City. In any case, there is nothing beyond Galveston except the services of Western Union. Mr Varney is able to confirm that such telegrams are passing to Herr Eckhardt. They are in code, but any coded texts in the archives of Western Union in Mexico City will henceforward be available to us. Perhaps we shall no longer be working blindfold after all.”
Within days there came into our hands at Baker Street, late one afternoon, a wire from Mr Varney. It had been forwarded by courtesy of Captain Guy Gaunt, the British Naval Attaché in Washington, who was also Naval Intelligence officer at the embassy. This wire accompanied the secret message which is known to history as the “Zimmermann Telegram”-and which the reader will find quoted as a coded text at the opening of this chapter. What follows is the best sense that Sherlock Holmes and I could make of it that evening.
We sat at either side of the work-table while Holmes made two copies of the coded message and passed one to me. I hardly knew how to start upon it but the keen energy of my friend’s brain began to illuminate the darkness of the cipher like forked lightning.
“Let us dispose of the first two groups of numbers, Watson. At the start, 130 is simply the number of the telegram and tells us nothing. The next, 13042, is the current prefix for communications in the German diplomatic code and tells us a good deal. Then you will see 13401, which identifies its source as the German Foreign Office, not the embassy in Washington. The source, if not the message, is genuine. The next item, 8501, confirms that this began its journey as a ‘Most Secret’ telegram from Berlin to Count Bernstorff, who has now forwarded it to Mexico City. Between them, such clues narrow our area of search a little.”
“We have intercepted no messages between Berlin and Washington in the past fortnight,” I said cautiously, “May this not be a hoax of some kind by the German intelligence service?”
He frowned and ran his pencil across the rows of numbers.
“I think not,” he said presently, “By its number this is a recent telegram which Zimmermann has passed to Bernstorff under the cover of the United States diplomatic code. Had Bernstorff not forwarded it to Mexico City, we should never have seen it. I believe that disposes of any hoax. Now then, there are recurring words in this cipher and I fancy they will show us the way”
His pencil was busy for a moment. Then he looked up.
“The framework of the telegram is in a cipher system we have encountered before, therefore what follows must be related to it. The message, I concede, appears to be encrypted according to a new code, that is the challenge, but the system which sustains it should be the same.”
He pushed his paper across to me.
“See here. In the preliminary instructions, we have 17214, which has previously been used for ganz geheim-strictly secret. Well that is no surprise-it is an old friend to me. And then, here, 6491 11310 18147. That is also familiar from previous use. Selbst zu entziffern-decipher this yourself. From there on the code has been varied and everything is a little opaque.”
I worked my way through it, trying to pick out any groups of letters whose position or repetition might help us to “get a lever” under the rest. Holmes took another approach.
“We know that Eckhardt in Mexico City must be able to decode it. It has been sent as a matter of urgency and therefore probably in a code that can be read by anyone who knew the previous one. Eckhardt is not allowed to refer the matter to his underlings, he can ask for no assistance, therefore it must be a familiar system to him.”
He bowed his head over the paper, the harsh white gaslight throwing the shadow of his aquiline profile on the wall. Presently he chuckled. His pencil was ticking the most frequently used words. He selected one of them.
“Here, here, and here, Watson. The group of numbers most frequently used is 69853. From its position, as compared with earlier messages which we have decrypted, it appears to be a noun, almost certainly a proper name. In an urgent and secret diplomatic message to the German Minister in Mexico City, what is that word likely to be?”
“I would say most probably ‘ Mexico.”’
“And here it is used with the cipher 5870, which also occurs just before it and immediately after it. The same 5870 occurs again two words further on. May I be kicked from here to Charing Cross if that is not a comma! What else can it be with such frequency? Now, such a series of commas would suggest a list, would it not? A list of three items in this case, the second of which is in two words. The second of those two words is ‘ Mexico.’ So we have a compound noun, the second half of which is ‘ Mexico.’ To me that strongly suggests ‘ New Mexico.’ Let us see.”
It was a characteristic leap of intuition. Beforehand the answer might have appeared an outside possibility. As presented by Holmes, it now seemed the only answer that made sense.
“In all probability it is a list of American states,” I said quickly.
“Excellent, Watson. New Mexico, with an item before and an item after. The one in front of it appears as five letters. Try “ Texas.” The one that follows it has four syllables. What state associated with Texas and New Mexico has four syllables?”
“ Arizona?” I replied hopefully.
“And what unites Texas, New Mexico, Arizona? All three were at one time part of Mexico and were lost to the United States by conquest. What plan has Herr Zimmermann for those states now?”
“To return them to Mexico? Impossible!”
“Not at all impossible, provided that there is a sufficient bargain upon the table. Another name 52262 recurs closely. You will recall that all nations in the last diplomatic cipher to be broken by us were reduced to five digits and I fancy this is one of them. Allow me the luxury of supposing that it stands for “ Japan.” You will recall that the battle-cruiser Asuma lately paid a prolonged courtesy call to Mexico, as the papers tell us. That news was contained in one of Bernstorffs previous ‘appreciations’ of the war situation. The ship was in Turtle Bay so long that she ran aground and had to be attended by other units of the Japanese fleet.”