"They instructed me to keep a watchful eye on you. We have missed things since your last visit." "That sounds like a jovial lie," said T. B. frankly. In the orderly instrument room they found an operator in attendance, and T. B. lost no time. "Call N.H.C," he said; and, whilst the instrument clicked and snapped obedient to the man's hand, T. B. opened his little exercise book and composed a message. He had finished his work long before any answer came to the call. For half-an-hour they waited whilst the instrument clicked monotonously. "Dash-dot, dot-dot-dot, dash-dot-dash-dot." And over and over again. "Dash-dot, dot-dot-dot, dash-dot-dash-dot." Then suddenly the operator stopped, and there came a new sound. They waited in tense silence. "Answered," said the operator. "Take this." T. B. handed him a slip of paper. As the man sent the message out with emphatic tappings, Captain Almack took the translation that T. B. handed to him. "To N.H.C. There is trouble here. I must see you. Important. Can you meet me in Paris to-morrow?" After this message had gone through there was a wait of five minutes. Then the answer came, and the man at the instrument wrote down unintelligible words which T. B. translated. "Impossible. Come to M. Will meet S.E. Have you got the book?" "Reply 'Podaba,'" instructed T. B., spelling the word. "Now send this." He handed another slip of paper across the table, and passed the translation back to the man behind him. "Is Gibraltar intercepting messages?" it ran. Again the wait, and again the staccato reply. "Unlikely, but will send round to-morrow to make sure. Good-night." As the instrument clicked its farewell, T. B. executed a silent war-dance to the scandal of the solemn operator, and the delight of the little captain. "T. B., you'll get me hung!" he warned. "You'll upset all kinds of delicate instruments, to say nothing of the telegraphist's sense of decency. Come away." "Now," demanded Captain Almack, when he had led him to his snug little office; "what is the mystery?" T. B. related as much of the story as was necessary, and the officer whistled. "The devils!" he swore. "The discovery I was trying to make," T. B. went on, "was the exact location of N.H.C. I asked him or them to come to Paris. As a matter of fact, I wanted to know if they were within twenty-four hours' distance of Paris. 'Impossible,' they reply. But they will come to Madrid, and offer to meet the Sud Express. So they must be in Spain and south of Madrid, otherwise there would be no impossibility about meeting me in Paris to-morrow. Where are they? Within reach of Gibraltar apparently, because they talk of sending round to-morrow. Now, that phrase 'sending round' is significant, for it proves beyond the shadow of a doubt exactly in what part of Andalusia they live." "How?"