"By Jove! no!" I gasped, as the true import of his words became instantly impressed upon me. "We have enemies, Teddy--you and I--without a doubt. We've made a discovery which is destined to upset the enemy's plans--therefore they want to wipe us, and all our knowledge, out of existence. That's what you mean--isn't it?" My chum nodded in the affirmative. "That's exactly what I do mean," he said in a hard, meaning tone. "Then my accident was due to treachery!" I cried angrily. "We must discover how it was all arranged." "Yes. Somebody, no doubt, tampered with your machine," Teddy declared very gravely. "Because I believe this, I've left it just as it was, and locked it up safely with a man to look after it. We'll examine it together later on, when you're fit to run over." Well, to cut a long story short, we did examine it about a week later. With Harry Theed, Teddy and Roseye, we made a very complete survey of every strainer, wing-flap hinge, nut-bolt, taper-pin, eye-bolt, in fact every part of the machine, save the engine--which was quite in order and practically undamaged. For a whole day we worked away, failing to discover anything, but late in the afternoon I noticed one of the bolts missing, and called the attention of both my companions. "By Jove!" exclaimed Teddy. "Why, that's the weak spot where the plane must have buckled!" Then, bending closer to the hole in which the missing steel bolt should have been, he cried: "Look! What do you make of this--eh, Claude?" I bent eagerly to where he indicated, and there saw something which caused me to hold my breath. In the hole where the steel bolt should have been was a plug of broken wood! Wood! The truth became, in that instant, quite plain. The tested steel bolt, which was most important to secure the rigidity of the aeroplane, had been withdrawn, and in its socket a plug of wood had been placed by some dastardly and unknown enemy! The Invisible Hand, of which I had spoken so many times, had very narrowly sent me to my death! Who could have tampered with my machine? All four of us stood gazing at each other, aghast at the discovery of that wicked plot against my life. My escape had been miraculous. I had risen easily from the ground, the wooden bolt holding the plane in position, but as soon as I had attempted to turn, strain had, of course, been placed upon the machine, and instantly the wood had snapped, so that I had come down to earth like a log. "If there is a desperate plot against me, Roseye," I said, looking straight at her, "then there is, surely, a similar one against you, and also against Teddy. Our enemies are desperate, and they know a good deal--that's certain. Perhaps they have somehow learnt that we four possess the secret of how the Zeppelin menace can be combated. No secret however is safe from the owner of the Invisible Hand. Hence, if an attempt is made to send me to my death--attempts will also be made against you both."