“We have a pretty good idea of the traitor in the department concerned, and he is now safely under lock and key. Unfortunately the mischief was done before he was even suspected, and the closest inquiries have failed to unearth any of his associates who would be regarded as in the slightest degree doubtful. It looks very much like a case of a hitherto thoroughly reliable man yielding to a sudden and overpowering temptation, while the real culprit—the man who pulled the strings—remains undiscovered. No doubt Count Wedell and his precious propaganda department have a first-class man at work, and they have so cleverly covered up the tracks that the method of their latest coup remains a mystery. It is perfectly obvious that the subterranean work of Germany is even now proceeding in France, Italy, and Great Britain.”

“Exactly, mon cher Sant. And you must take this particular matter in hand at once, and try to discover at least one of the fingers of what your good friends across the Channel call so appropriately ‘the Hidden Hand.’ For myself, I feel quite sure that at last, after much seeking, we have alighted on the source of the whole affair, so far as England and France are concerned.”

Our conversation had taken place at Armand Hecq’s house out at St. Germain, beyond Paris. I had come post-haste from Lausanne, where I had been engaged with Poiry—an ex-agent of the Paris Sûreté—upon another matter. An urgent telegram from Hecq had warned me that the new business was most important, hence I had lost no time in answering his summons.

It was a warm afternoon, and we were seated out on the terrace overlooking the pretty garden, which was the hobby of the most remarkable and resourceful secret agent in all Europe.

To outward seeming Armand Hecq was a prosperous Parisian financial agent, whose offices in the Boulevard des Capucines, opposite the Grand Hôtel, were visited by all sorts of persons of both sexes. None, excepting those “in the know,” suspected that these handsome offices, with the white-headed old concierge wearing the ribbon of 1870, were in reality no mere financial establishment, but the headquarters of the international espionage of the Allies. None realised that the crowds of “speculators,” who flocked thither in the pursuit of ever-elusive wealth, included among them dozens of men and women who day by day carried their lives in their hands in their never-ending warfare with the unscrupulous and resourceful agents of Germany. None dreamed that to the busy staff finance was a mere side-line; that their real interest was not the daily fluctuations of the Bourse, but the thread of Hun intrigue which ran through all the crowded life of the gay city, and was nowhere stronger than in the department of finance.

“Now, Sant,” said Hecq abruptly, after we had sat silent for a few minutes while I ran over in my mind the essential facts of the new and tangled case. “You have seen the photographs and the dossier, and you understand the position. What is your opinion?”

“There can be but one,” I answered leisurely. “Before the war, Jules Cauvin, of Issoire in Auvergne, was a struggling corn-merchant. He has since, in some unaccountable way, blossomed out into a man of wealth, and has purchased an important estate with money which has come from some mysterious source. Constant payments appear to reach him from a firm of motor-engineers somewhere in England. In his sudden prosperity he has bought a villa at Mentone, where he lives during the winter with his wife and family, and he is often seen at the tables at Monte Carlo. Among those who have stayed with him at the Villa des Fleurs was the Russian Colonel Miassoyedeff, who was recently hanged as a spy of Germany. There can be only one conclusion from all this.”

“Ah! my friend. I see you have mastered the essentials,” said Hecq approvingly. “Now Cauvin and all his friends are under the strictest surveillance; the question is how we are to secure evidence to convict him of the espionage he is undoubtedly concerned in. We can arrest him, of course, at any moment; he has no chance whatever of getting away. Every letter he sends or receives is opened and photographed, yet, up to the present, he has been too clever for us. If he were put on trial for espionage to-morrow, not even his friendship with Miassoyedeff would prevent him from being acquitted. We have no evidence against him whatever, beyond the fact of his sudden wealth, and that, even in these times, is not enough.” And Hecq looked at me with an appeal in those soft, strange eyes of his. I could see that the case of Cauvin presented itself to him as supremely important, and that it must be solved if we were ever to grapple successfully with the mysterious, deadly influence whose workings we could feel and trace all around us, but the real wielder of which appeared constantly to slip through our fingers.

“I quite understand you,” I said, sipping the little glass of Cointreau he had offered me. “There is only one thing to be done. We must find that finger of the Hidden Hand in England.”

“Exactly, my dear Sant,” exclaimed my chief, with a quick gesture of approval. “We seem to be losing ground day by day. Why? At all costs the position must be retrieved. You will want Madame Soyez to help you. Let me see; she is at present in England. I sent her across only a week ago to make some inquiries. Excuse me a moment while I speak to Guillet,” and he left me to go to the telephone.