"That's what I wanted to know," remarked Peter gratuitously. "Now, Uncle Brian, we'll gag and bind this gentleman, to be left till called for." Peter proceeded with the operation so rapidly and deftly that it left Uncle Brian wondering where his nephew had acquired that knowledge. In a very few moments the Rioguayan was trussed like a fowl, his sash and belt coming in very useful for the purpose. "Now a cartridge, Uncle Brian," continued his relative. Uncle Brian handed him one of the rifle cartridges. This Peter wrapped in a handkerchief. "Open your mouth, old son," he said. The "old son", although ignorant of English, obliged instantly. It was patent that he, too, had had experience in the gentle art of gagging. "And that's that," concluded Peter. "Now for the next act of the matinee. We'll kick off from our hiding-place. It's only an eight-foot drop to the beach, and a jolly sight quicker than scrambling down the cliff. I'll take the rifle, please." Silently and cautiously the two men descended the gully until they reached the breastwork separating the rift from the beach. Peter peered cautiously in the direction of the flying-boat. The Rioguayan captain was still at his post in the pilot's seat. He was wearing his leather flying-coat but had thrown back the flaps. He was a swarthy, thick-lipped man with hulking shoulders and a head set well forward--altogether a brutal type of humanity. "It's like potting a sitting rabbit," thought Peter, as he slipped a cartridge into the breech of his rifle. "It's not giving the fellow a ghost of a chance." Yet, his compunction notwithstanding, Peter's hands were as steady and his eye as clear as an experienced hunter's. It was the first time in his life that he had had a human being covered with a rifle--but it was the only way. Deliberately he pressed the trigger. The Rioguayan captain did not appear to move. Peter was beginning to think that he had missed, when the man leant forward until his head rested on his arms on the deck of the fuselage--to all appearances as if he were asleep. Without hesitation, the Englishmen vaulted over the ledge of rocks on to the beach and ran towards the flying-boat. They fully expected to find their way barred by the two mechanics; but the latter had either not heard the shot, or, if they had, had taken it as one of the many fired by the searchers on the island. [Illustration: PETER TACKLES THE SENTRY _Page_ 126] Gaining the pilot's cabin, Peter peered down the hatchway into the engine-room. The place was empty. Hurrying aft, he found the two mechanics in the motor-room, where the twin engines driving the after pair of propellers were situated. At the sight of a couple of automatics thrust down the hatchway both men raised their arms with commendable celerity. "Up--you!" ordered Uncle Brian, indicating one of the engineers. The fellow complied, his olivine features grey with terror.