“Well, we did have an involuntary bath,” admitted Rob, and he went on to tell just what had happened.

“Jove!” exclaimed Mr. Mainwaring when he had finished, “this is getting interesting, and perhaps explains many annoying things that have been happening about here recently. Derrick booms have collapsed without apparent cause and an investigation has shown that acid has been poured on the supporting ropes by some malignantly disposed persons. Blasts have been set off prematurely, narrowly avoiding injury, and the work has been delayed by many such tricks. It wouldn’t surprise me a bit if your friend Jared and the Latin Americans who are interested in delaying the canal construction are at the bottom of this. I’ll dispatch men at once to get hold of this chap Jared and we’ll make him confess all about it.”

As he spoke there was a sudden crash behind him as a workman, who had been standing close to him and who must have overheard every word, dropped a heavy bucket. They all faced round and saw a man shuffling off rapidly. Something familiar about him struck Rob, but for the life of him he could not place the man. It was not until later that he recalled where they had seen him before. He was the man who had driven them to the ruins of old Panama on that memorable morning, and who must have heard some of their talk. But what was he doing on the canal work? Was he allied with the forces that were trying to defeat the completion of the canal? Had he told the plotters of what he had overheard and warned them that vigilant retribution was on their trail?

All these were questions that for the time had to wait. Rob decided not to say anything just then. After all he might have been mistaken. In the meantime the searchers sent out after Jared reported that they could not find him. Undoubtedly after venting his malice on the boys he had made off. Rob was not mistaken in his identification of the cabman. The fellow was allied with the plotters by close ties both of nationality and sentiment. He had been set to driving a hack in Panama so that he might carry on his spy work without being suspected. It was by chance that the boys had happened to take his cab. But what he had overheard that day had caused him to hasten to the dam and inform his confederates, who, as Rob had guessed, were constantly about there disguised as workmen.

In that vast enterprise, employing thousands of laborers, it was a simple enough matter for any able bodied men to obtain employment, and no questions were asked so long as the laborer proved able to earn his pay. At dinner time Mr. Mainwaring was unusually silent. There was no question in his mind now but that there were plotters mingled in among the workmen. That night orders for extra vigilance in patroling the dam were issued, and that night, also, Mr. Mainwaring announced that he intended to start the next day on his search for the troublesome tributary of the Chagres River which it was his intention to devise a means to control.

As may be imagined, this was great news to the boys, and they passed an all but sleepless night in their room in Mr. Mainwaring’s bungalow, which stood in a row of “gold-men’s” houses, among which it was the largest and best finished.

The boys’ equipment had been brought up from Panama with them and was, as usual, all in readiness for instant transportation. These Boy Scouts lived up to their “Be Prepared” motto all the time, and to the finest detail. When their camping equipment had been packed up on the submarine island everything had been stowed away with military precision so that they knew, without going through a lot of troublesome overhauling, that everything, down to their small pocket water filters, was in its right place.

A wagon transported their goods and chattels to the landing place on the Chagres the next morning, right after an early breakfast. Mr. Raynor was to accompany his chief in the capacity of assistant, and the surveying instruments and other paraphernalia almost filled one of the odd native canoes they were to use. Another canoe held the camping outfits. But they were not to paddle their way laboriously up the swiftly flowing river.

To the delight of the boys a light draught launch, fitted with powerful engines and a spidery stern paddle wheel, was to do the towing while they took it easy. This suited Tubby down to the ground, and Rob’s cup of satisfaction was full to the brim when he learned that he and Merritt were to alternate as engineers. As we know, both boys were familiar with the management of gasolene engines, and they gazed with approval at the fourteen horse-power, twin-cylinder engine of the Pathfinder, as the launch was called.

Before they left, the chief of the Gatun Guards, as the police that watched the big dam were called, reported to Mr. Mainwaring that nothing suspicious had occurred during the night and also that no trace could be found of the men wanted. This was disappointing, but the boys were so keyed up with the expectation of the wonders that awaited them in the tropical forests through which the Chagres wound its way on its higher reaches, that they gave but scant thought to Jared and the plotters.