My Dear Estair,—I now have Salt's complete report before me, and there seems to be no doubt that the proposal I have formulated is feasible, and the——
Written without vowels, stops, capitals, or spaces, this gave a very serviceable cryptograph, but there was an added safeguard. After completing the first line the writer moved a shift-key and brought another set of symbols into play—or, rather, the same symbols under a different arrangement. The process was repeated for the third line, and then the fourth line returned to the system of the first. Thus three codes were really in operation, and the danger of the key being found by the frequent recurrence of certain symbols (the most fruitful cause of detection) was almost overcome. Six identical machines were in existence. One has been accounted for; Sir John Hampden had another; and a third was in the possession of Robert Estair, the venerable titular head of the combined Imperial party. A sociable young publican, who had a very snug house in the neighbourhood of Westminster Abbey, could have put his hand upon the fourth; the fifth was in the office of a super-phosphate company carrying on an unostentatious business down a quiet little lane about ten or a dozen miles out of London; and the sixth had fallen to the lot of a busy journalist, who seemed to have the happy knack of getting political articles and paragraphs accepted without demur by all the leading newspapers by the simple expedient of scribbling "Urgent" and some one else's initials across the envelopes he sent them in. Communications of the highest importance never reached the stage of ink and paper, but the six machines were in frequent use. In bonâ fide communications the customary phraseology with which letters begin and end was not used, it is perhaps unnecessary to say. So obvious a clue as the short line "kbeljsl" at the head of a letter addressed to Estair would be as fatal to the secrecy of any code as the cartouched "Cleopatra" and "Ptolemy" were to the mystery of Egyptian hieroglyphics. That Salt wrote it may be taken as an indication that he had another end in view; and it is sometimes a mistake to overrate the intelligence of your opponents. When the letter was finished he put it away in his pocket-book, arranged the fastenings of both safe and desk so that he could tell if they had been disturbed, and then went home.
The next morning his preparations advanced another step. He brought with him a new letter copying-book, a silver cigarette-case with a plain polished surface, and a small jar of some oily preparation. With a little of the substance from the jar he smeared the cigarette-case all over, wiped away the greater part again until nothing but an almost imperceptible trace remained, and then placed it carefully within his desk. The next detail was to write a dozen letters with dates extending over the last few days. All were short; all were quite unimportant; they were chiefly concerned with appointments, references to future League meetings, and the like. Some few were written in cipher, but the majority were plain reading, and Salt signed them all in Sir John's name, appending his own initials. To sign the long letter which he had already written he cut off from a note in the baronet's own handwriting the signature "John Hampden," fastened it lightly at the foot of the typewritten sheet, and then proceeded to copy all the letters into the new book. The effect was patent: one letter and one alone stood out among the rest as of pre-eminent importance. The completion was reached by gumming upon the back of the book a label inscribed "Hampden. Private," treating the leather binding with a coating of the preparation from the jar, and finally substituting it in the safe in place of the genuine volume. Then he burned his originals of all the fictitious letters and turned to other matters.
It was not until two days later that Mr Tantroy paid Salt a passing visit. He dropped in in a friendly way with the plea that the burden of his own society in his own room, where he apparently spent two hours daily in thinking deeply, had grown intolerable.
"You are always such a jolly busy, energetic chap, Salt, that it quite bucks me up to watch you," he explained.
Salt, however, was not busy that afternoon. He only excused himself to ring for a note, which was lying before him already addressed, to be taken out, and then gave his visitor an undivided attention. He was positively entertaining over his recent journeyings. Freddy Tantroy had never thought that the chap had so much in him before.
"Jolly quaint set of beggars you must have had to do with," he remarked. "Thought that you were having gilded flutter Monte Carlo, or Margate, or some of those places where crowds people go."
Salt looked across at him with a smile. "I think that there was an impression of that sort given out," he replied. "But, between ourselves, it was strictly on a matter of business."
"We League Johnnies do get most frightfully rushed," said Freddy sympathetically. "Bring it off?"
"Better than I had expected. I don't think it will be long before we begin to move now. You would be surprised if I could tell you of the unexpected form it will take."