"He is a master-mind, and a highly dangerous personality; dangerous because he is so clever. And now that he has secured a few daring airmen for his tools, there is no end to the possibilities which his evil genius may accomplish before he and his crew are run to earth," replied Captain Keane. "I know it, I know it--look here!" and the colonel handed him the batch of cables and wireless messages which showed how the _Scorpion_ had already got to work. "H’m! and there will be worse to follow," added the airman after he had glanced through the list. "Now, tell me briefly what you have found, Keane, after which we must get to work to devise some immediate plan to thwart these aerial brigands. But first take off your flying gear, and sit by the fire, for you must be hungry, tired and numbed after that cold night ride." Then, ringing for his attendant, he ordered up more strong coffee and sandwiches. "Thanks, Colonel, I will not refuse. It was indeed a cold ride, and we had no time to get refreshments before leaving the aerodrome at Cologne this evening," said Sharpe, as he divested himself of his heavy gear, sat by the fire and enjoyed the coffee which soon arrived. A few moments later, the three men were engaged in serious conversation, although the hour of midnight had long since been tolled out by Big Ben. "You sent me," Keane was saying, "to discover the whereabouts of this great German engineer and man of science, this brain wave whose perverted genius is likely to cost us so dear." "And you were unable to find any trace of him?" interposed the chief. "Well, we were unable to come into contact with him, for we found that since peace was concluded he had vacated his professorial chair at Heidelberg University, where he had been engaged for some considerable time, not only on some mechanical production, but in an attempt to discover some unknown force, evidently a new kind of highly compressed gas to be used for propulsive purposes." "Had he been successful?" "That, it was impossible to find out during our short stay over there," replied Keane, "but I discovered from someone who had been in close touch with him just about the time peace was signed, that he had expressed himself in very hopeful terms." "Was he a very communicative type of man, then, did you learn?" "No; on the contrary, he seldom spoke of his work, but on this occasion, when he communicated this information, he was very much annoyed at the defeat of Germany, and considered that his country had been betrayed into a hasty peace." "And what happened to him after that?" asked the colonel. "Shortly afterwards he disappeared completely, taking with him all the apparatus connected with his research work, also a highly skilled mechanic who had been specially trained by him for a number of years. But he left not a trace of himself or his work," said the captain, pausing for a moment to light a cigarette.