During that Christmas season of 1916 and into the New Year, Sherlock Holmes was a stranger in Baker Street. If he slept in his own bed, he was gone before breakfast and absent until after midnight. Often he slept on a camp bed at the Old Admiralty Building, in a shabby panelled office allotted to him by Signals Intelligence. When grander accommodation was offered, he declined it. He worked alone in his “cubby hole” and there was little sign of him elsewhere in the building. The departure of the U-boats on their voyage kept our wireless interception busy day and night with ciphers to be decoded.
The New Year brought us the freezing January of 1917. I had taken three days leave to go alone to the Exmoor cousins at Wiveliscombe. I returned to Baker Street very early one morning, before the office workers were at their desks. An overnight sleeper had brought me on the train from Taunton to Paddington. There was no sign of Holmes in our rooms. It appeared as if he had not been in the house since my departure. I summoned Mrs Hudson.
“Why, Dr Watson, sir, I thought he must have gone down to Devon with you, after all. There’s been no sign of him here since you left.”
I called a cab off the rank and set off at once for Whitehall. If Holmes had been away for three days and two intervening nights, it must be at Room 40. When I arrived, only those who had been on watch since the day before were still there and the new watch had not yet taken over. I went to the Watchkeeper’s Office. Here the printed intercepts arrived through pneumatic tubes. A row of clocks told the time across the world from London to New York to Tokyo and back to Berlin. Closed circuit telephone lines ran to the Director of Naval Intelligence, the War Office, Special Branch at Scotland Yard, and the Prime Minister in Downing Street. The waste-paper baskets were usually full of pages, crumpled and discarded during the long night, all of which would be emptied into the Horse Guards incinerator by Royal Marine sergeants.
As a rule, several of the night watch would sit at their desks until 10am. In the morning light, their faces were pale from exhaustion and drawn from lack of sleep, eyes staring unnaturally bright from the dark shadows of their sockets. Even then, if necessary, they would wrestle for several hours more with some new naval or diplomatic cipher which had been changed at midnight in Berlin or Vienna.
This morning, Holmes was in the Watchkeeper’s Office alone. He sat in a wooden chair, the desk before him clear, head back, arms folded and eyes closed. Yet he was not asleep. His eyelids lifted as I came in.
“Where are the others?” I asked.
“They have gone,” he said wearily, “There was no purpose in staying. They had no work to do.”
“And the ciphers?”
“They have vanished.” He stood up. “The diplomatic ciphers between Berlin and Washington, that it is say everything that matters in the present state of affairs, have disappeared from the ether. So far as we are concerned, they are neither being sent nor received. There have been no intercepts for the past two days.”
I stared out of the window, across the mist of St James’s Park where two Jersey cows were grazing on the frosted grass that stretched between us and Buckingham Palace. I tried to make sense of what he had just said.
“Surely the signals are being sent. Now, of all times, when Wilson and Zimmermann are trying to avoid war. Zimmermann must be in contact with Bernstorff and their Washington embassy.”
Holmes sighed.
“Not through his own signals. Negotiations between the two countries are at a delicate stage. The last messages that we received merely confirmed that Chancellor Bethmann-Holweg had agreed to consider President Wilson’s fourteen-point proposal for a general peace on all fronts. I have a private assurance of that, from Edward Bell at the American Embassy. Bell tells me in confidence that President Wilson authorised the use of America ’s own diplomatic telegraph for transmission of German peace proposals in code.”
“And what of the U-boat fleet heading for the American coastline?”
“So far as we are concerned that has vanished off the map. So far as the Americans know, it never existed. For a time, it was communicating through Sayville, Long Island, disguised in the codes of commercial or steamship company telegrams. That has ceased.”
“How will Berlin ’s signals carry to Washington?”
“During the present negotiations, Zimmermann has requested that his own telegrams to Robert Lansing at the State Department shall be transmitted from Berlin with those of the American Embassy, in the American diplomatic code. The route is through neutral cables from Berlin to Stockholm, then to Buenos Aires and so to Washington. Wilson ’s Ambassador in Berlin, James Gerard, has agreed.”
“To transmit German diplomatic intelligence? Preposterous!”
“Perhaps. However Gerard and Secretary Lansing have accepted this, apparently on Wilson ’s instructions. Still worse, they have accepted Zimmermann’s insistence that his telegrams to Bernstorff must be transmitted by the Americans in the usual German diplomatic code-undeciphered-so that they remain confidential to Bernstorff. These telegrams are forwarded, unexamined, from the State Department to the German Embassy. Lansing and Wilson have no idea of the contents. Negotiations between the two countries are too delicate to permit the risk of interception in London or elsewhere.”
“It is unthinkable!”
“So is war,” said Holmes gloomily, “To Wilson, war is an abomination. If he can end it, why not allow Zimmermann this small concession? Zimmermann must send diplomatic telegrams to his ambassador in Washington anyway. Wilson does not want the British or the French eavesdropping at this point.”
“Why can we not eavesdrop through our own efforts?”
“Because we should have to break the American diplomatic code, before we can get at Zimmermann’s telegrams. Imagine a friendly power discovering that we had deliberately broken its code and were reading its confidential messages. In any case, Balfour at the Foreign Office has categorically forbidden it-at eight o’clock last night. We can only sit here and see if the ciphers in the German Diplomatic Code-13042-resume.”
“Well here’s a pretty pickle!” I said helplessly.
“Not quite. Stockholm is a link in the route. I have been trying my hand at the recent Swedish ciphers in our archives-so far without much reward. They have never merited attention before. I have established, however, that the new Swedish envoy in Mexico City has German sympathies. In one case, he has so far forgotten himself as to send in plain text an appreciation of the situation in Mexico. Unforgivably careless.”
Holmes drew a transcript from his pocket and read out what he had copied.
“Dated 1 September 1916. President Carranza, who is now openly a friend to Germany, is willing to provide support if necessary, and if possible, for German submarines in Mexican waters.”
The chill that ran through my blood was no figure of speech.
“For the U-boats from Wilhelmshaven!”
“It had clearly been arranged before they sailed.” Holmes continued to read the Swedish envoy’s report.
“The Imperial German government proposes to employ the most efficient means to annihilate Britain as its principal enemy. Since it intends to carry its operations across the Atlantic with the object of destroying its enemy’s merchant fleet, it will need shore bases to fuel and supply the submarines. In return, Germany will treat Mexico like the free and independent nation which it is.”
Holmes paused.
“There is a good deal more but that is the gist of it.”
I looked round the dim, gloomily-boarded watchroom.
“And the Americans know nothing of this?”
“No one else knows as yet. Arthur Balfour at the Foreign Office fears that if we reveal the contents of the Swedish telegram now, senior figures in America will treat it as a British hoax, designed to draw them into the war. In any case, it is no more than the opinion of one diplomat. No more than a foreign correspondent in Mexico City might write in his newspaper.”