“H’m!” he grunted. “Very wily of De Gex to get the police to keep an eye upon me. If I’m not careful I shall suddenly find myself under arrest as a suspicious person who is in the habit of loitering in the vicinity of the great financier.”

“Yes,” I agreed. “This seems to put an end to our present activity—does it not?”

“Well, he apparently knows that we are watching,” Hambledon said. “What a pity we cannot tell the police all we know.”

“If we did we should not be believed, and, moreover, they wouldn’t hear a word against the great man who is such a friend to Spain. Money buys reputation, remember. Nobody knows that better than De Gex.”

Hambledon was standing at my bedroom window looking thoughtfully down upon the Puerta del Sol with its crowd of hurrying foot-passengers.

“It seems a miserable ending to all our careful surveillance upon Suzor—doesn’t it?” he grumbled.

“True, it does. But now that the pair are on the alert I cannot see that anything can be gained by remaining in Madrid longer,” I pointed out.

“Then you intend to give up the quest for the truth?”

“Not by any means,” I replied quickly. “I intend, at all hazards, and at all costs, to still fathom the mystery. What we have learned since we came to Spain puts quite a different complexion upon matters. We are now in possession of certain facts concerning De Gex—facts of which we had no suspicion. We had never dreamed that to further his ends he did not hesitate to employ a notorious criminal to commit murder with malice aforethought. Neither did we know anything of his financial dealings with the Spanish Ministry of Finance, or his partnership with the Conde de Chamartin, or that the drug he used upon poor Gabrielle and myself was the obscure but most deadly and dangerous orosin. All these are points which may in the near future be of greatest advantage to us. Therefore we must not despair. Let us take courage and continue to probe the mystery—for the sake of poor Gabrielle Tennison,” I urged. “Let us act as quietly and discreetly as our enemy is acting, and we may yet attain success!”