Much to the chagrin of Tom and Ned, but to the huge delight of Jupe, who had no great fancy for the work in hand. Jack and Captain Andrews were to be the ones to do the reconnoitering. Tom and Ned were ordered to stand by the Flying Road Racer and be ready for any sudden development that might occur. While Captain Andrews and Jack were absent, it would be the others’ duty also to refill the gas bag, so that the aero-auto might be ready for an instant ascent in case of need. These preparations completed, the two who were to assume the most risky part of the night’s work each selected a fully loaded gas-gun. In addition. Captain Andrews carried an automatic revolver; but it was on the former weapons that they would largely depend. There remained nothing more but the leave-takings, and the fervent wishes for success in the daring enterprise, coming from the lads who were to be left behind. These final ceremonies being disposed of, the grizzled old sailor and his young companion set off. Tom and Ned watched them till the shadows of the forest swallowed them up. By good fortune, the two, upon whom so much depended, struck a trail almost immediately after their first plunge into the blackness that prevailed under the tropical trees. The path had evidently been used by the laborers who had made the clearing beyond. It was a broad, well-defined track, and their progress was rapid and almost noiseless. Neither of them spoke as they made their way along the path. The situation was too critical for words, and Jack crept along behind Captain Andrews, hardly daring to breathe. He was on the tip-toe of excitement and anxiety, as was natural. At the end of the trail they were following’ lay either success or dire failure. There was no middle ground. In the event of their failing in their mission. Jack could not disguise from himself that the consequences would be awful indeed. He had come in contact with Herrera only once, but that single occasion had amply sufficed to show him the character of the man. From time to time, as they advanced, they paused and listened intently. But, except for the drone of the night insects of the jungle, and the occasional scream of a nocturnal bird, there was no sound other than the sighing of the breeze in the tree tops far above. There is no place more mysterious than the jungle at night. The dense thickets seem to the nervous traveler to hold all manner of hidden perils. Some of these are not altogether imaginary, either. The cunning, cruel jaguar, the huge serpents, and a score of other dangers lurk in the shadows. Fortunately, neither of our friends was burdened with sensitive nerves, and it was well they were not, for their errand was not one for timid folk to embark upon. They glided along after all these pauses, making as fast time as possible. All at once Captain Andrews, who was in the lead, as we know, stopped abruptly. So abruptly, in fact, that Jack almost collided with him. “What’s the——” began Jack.