"It is just possible," he murmured to himself, "that the two things are connected--the disappearance of this eminent scientist and the appearance of this extraordinary flying machine." Then he switched off the light, and returned to the sheaf of papers and documents on his desk. He sorted out one and placed it on top; it was a decoded message, received some days ago from one of his agents at Constantinople. It ran as follows:-- "Mysterious aeroplane, phantom-like in appearance, passed over here yesterday flying at terrific speed. All our signals disregarded. No navigation lights showing. Our fast scouts gave chase but left hopelessly behind. Came from direction of Adrianople, crossed the Bosphorus, and disappeared rapidly flying south-east. Time shortly after sunset. AERIAL, CONSTANTINOPLE." "That is three days ago," continued the Colonel, still thinking aloud, "and here are four similar messages from other sources showing quite plainly the route taken. Great Heavens! if I were not tied to my desk in this place, I would take the fastest scout in the country and chase this infernal night-wizard myself." A soft tap at the door startled the Commissioner, for during the last three days he had become highly nervous; this affair was getting on his mind, but he recovered himself instantly and called out in a deep voice:-- "Come in!" The door opened softly and his confidential secretary entered, and announced:-- "Two more cables and a wireless message, sir." "Anything from Keane or Sharpe yet?" demanded the chief. "Nothing, sir." "Then what are these confounded things?" "More about that aerial brigand, sir." "Let me see them," and Jones handed the messages to his chief. Consternation and alarm were both visible on the face of Tempest as he read the news. "So the devil has already got to work, Jones," he remarked, quoting from the sheets, laconic phrases such as "Oil tanks at Port Said burning for three days. Crew of mysterious aeroplane suspected." (Delayed in transit.) "Wireless station at Karachi utterly destroyed, after brief visit by strange airmen." The third was a wireless message which proved most disconcerting of all to the Commissioner. It announced that a silent aeroplane, showing no distinctive marks whatever, passed over Delhi "this afternoon" at a speed estimated at not less than three hundred miles an hour. The chief of the aerial police leaned back in his chair and groaned. "Three hundred miles an hour!" he gasped; "but the silent aeroplane idea is a fallacy. It is impossible with any type of internal-combustion engine. It must either have been too high up for the good people of Delhi to hear it, or its engines must have been shut off, or well throttled down. Bah! I know too much about aeroplanes to swallow that." Then rounding upon Jones, who was standing by awaiting instructions, he said sharply:-- "Did that second message go out to Keane?" "Yes, sir." "And there’s still no reply from him?"