Dick’s face hardened instantly.
“Get in, Yvette,” he said curtly.
Yvette stared in utter astonishment. This was a new Dick with a vengeance! All his usual graceful courtesy had dropped from him in the instant; the sheer fighting spirit was on top and Dick was, for the moment, the officer giving commands to his subordinates. His face was set like granite, and into the keen eyes there came a look Yvette had never seen there before. The cheerful, laughing “pal” had gone; in its place stood the fighting machine, pitiless and efficient.
For an instant the girl was almost on the edge of rebellion; then she turned, and, without a word, took her place in the machine. As she did so, she caught Dick’s eye. For an instant the stern face relaxed; then the iron mask shut down again.
For five minutes, while Yvette put on her leather helmet, Dick studied the plan which Jules showed to him by the light of a shaded lantern. When the Mohawk jumped into the air every detail of it was photographed indelibly on his brain.
For three thousand feet the Mohawk shot upward at a speed which left Yvette dizzy and breathless. Then they hung motionless, as Dick peered anxiously earthward. Were they high enough?
With a smothered exclamation Yvette pointed downward. Far below them a light was circling swiftly, darting hither and thither like a will o’ the wisp. No mail plane would behave like that. Dick decided that here was his quarry.
Silently the Mohawk came down till it was not more than five hundred feet above its unsuspecting prey, the loud drone of whose engine came clearly on the air. Dick swung round in a circle, following every movement of the machine below, with a swift precision which Yvette keenly appreciated.
Dick had made up his mind that the offices above the aeroplane shed probably held the key to the problem they had to solve. He knew he could destroy the machine itself. But that would not be enough if the plans remained intact; a new machine could quickly be built. If he could destroy the plans, on the other hand, there would be at least a lot of delay, which would enable the French agents to perfect their plans for discovering the secret. In all probability, he reasoned, the office would serve as the draughtsmen’s workroom, and if this were so, a well-placed bomb might destroy the labour of months.
So he watched and waited, until at length they saw the German aeroplane going home. It came down in a wonderfully steep descent which was enough to tell Dick that the Germans had indeed made a discovery of great importance, and landed so slowly that Dick could hardly believe his eyes. But, at least, he saw enough to be sure that the descent was not the vertical drop of his own helicopter. His secret remained his own!