Peter took another look at the flying-boat. He could see the officer in charge sitting up in the for'ard cockpit with a rifle laid upon the decking by his side. There was no one else visible, but in front of the Rioguayan was an automatic gun somewhat resembling a Colt, with its muzzle pointing ominously in the direction of the way down the cliff. "We'll have to rush the 'bus, Uncle," said Peter in a low voice. "It's our only chance." Uncle Brian nodded, and raising the haversack from the ground, slung it over his shoulder. "Right," he whispered. "Lead on, but keep a sharp look-out in case there's a man on guard on the cliff. If there is, no firing if it can be avoided, mind." His nephew gave a sign of assent and replaced his automatic, taking the precaution of leaving the flap of the holster unfastened. Then, with his uncle close at his heels, he crept cautiously along the gully, till he arrived at the slightly rugged ground adjoining the brink of the cliff. As Peter had expected, there was a sentry posted within ten paces of him. The fellow had discarded his flying kit, which was not to be wondered at, seeing that the temperature was somewhere in the region of 120° F. Evidently taking it for granted that, as his comrades and the bloodhound had swept the ground in the neighbourhood of his post, he could "stand easy", he even went so far as to commit the grave military crime of parting with his rifle, for the weapon was resting against a rock. His back was turned to the two Englishmen and--a fact that Peter noted with intense satisfaction--he was rolling a cigarette. Like almost every person of Latin descent, the fellow was an adept at that task, the cigarette when made being almost semicircular as regards its shape. Then, producing a large box of sulphur matches, he proceeded to set light to the "smoke". That was the opportunity which Peter was waiting for. He reckoned on the sulphurous fumes causing a little discomfort to the smoker, or at least his attention would be concentrated upon lighting the cigarette, to his own undoing. Peter had already counted the men engaged in following the useless trail. There were seven, strung out in an irregular line, and by this time quite a quarter of a mile away. As stealthily as a cat, Peter approached the careless sentry until he was within a couple of yards of him. Then he sprang. His love of Rugby football had taught him how to "tackle his man low". Before the Rioguayan could utter a sound or realize what had happened, he was lying half dazed upon the ground, with Peter pinning his arms and Brian Strong pressing the muzzle of an automatic gently against the fellow's temple. "Ask him," said Peter, "how many men are on board the flying-boat." Uncle Brian obliged, backing up his request with a slightly stronger pressure of the cold ring of the automatic's muzzle. "The captain and two mechanics," was the tremulous reply.