In the cool water, Bob soon forgot his hurts. Coming out on the shore he took stock of the damage that had been done. His hands were sore and stinging sensations from different parts of his body told him that he had not come off scot-free. Such clothes as he had on were ruined and he knew that in all probability he was such a sight that his own father would not have recognized him if they had met face to face.

Assured that he had suffered no damage that was really serious, Bob gave some thought to other pressing matters. Since no one had appeared after he had broken out of the hut, he must have been right when he figured that Harper had had no intention of sticking around all night.

But because no one was around now, it did not mean that no one would be. Probably the best plan would be to go and go quickly before either Wesley or Harper decided to come down and bring their captive food and water.

“Some surprise those chaps will get!” laughed Bob to himself as he started down the river in the general direction of the dam. “I wonder what they’ll do. Hit the high spots probably getting away from this neck of the woods!”

It took longer to get back to camp than he had supposed, for he was afraid to leave the river which served as his guide. Therefore it was nearly noon when a bend of the river showed him the dam.

Fearing that his appearance would cause a sensation, Bob waded and then swam across the shallow river and struck off to one side, meaning to circle around to the upper camp. Then he could slip into the Quarter-house by the back way.

This maneuver was executed without mishap and the only person who saw him go in was the Mexican cook, who paid little attention.

“I guess he thinks the Gringo got mixed up with a charge of dynamite!” was the boy’s reflection as he scuttled up to his room.

It was not long before he presented himself, washed and changed, at the general offices. As he went in he asked the girl at the telephone if Mr. Whitney had returned.

“Not yet,” was the crisp reply, “but Mr. Taylor wants to see you. Jerry King didn’t show up to-day either and he’s worried.”

So Jerry had not come back. It did not surprise Bob much, but it meant that Jerry had now openly allied himself with the other faction. The fight was to be in the open, from now on. Coming back to himself, he asked: “Where’s Mr. Taylor then?”

“In his office.”

He found Mr. Taylor busy over some blue prints. The engineer looked up as he entered and Bob at once saw that the man was angry. His first question proved it.

“What the dickens do you mean by not reporting this morning? Just because Mr. Whitney is away, do you think you can take a vacation when you feel like it? And King, too; wait till I get hold of him! But what have you got to say for yourself, young man?”

“I couldn’t help it—”

“Couldn’t help it!” exploded the irate man. The total responsibility for the project had fallen on him for the past few days and it had made him nervous. “Of course you could help it. You’ve got to help it if you belong to the Service!”

Bob waited until the storm had passed and then asked calmly:

“Has the Chief told you he suspects trouble with the Mexicans?”

The man looked at the boy sharply but made no reply. From his manner Bob was sure that Mr. Taylor knew but did not wish to confess his knowledge. Figuring that his silence was equal to an assent, Bob went on:

“Mr. Whitney told me something about it and the reason I’m late to-day is that I got mixed up in the mess—”

This startled Mr. Taylor.

“You—you’ve found out something?” he stammered eagerly.

“Yes,” answered Bob, “I have. I wanted to tell Mr. Whitney personally about it but as things are likely to happen right off, I think we’d better get busy without him.”

Rapidly Bob sketched out what he had learned during the past few days and related briefly the adventure that had befallen him the day before. As to Jerry’s part in the mix-up, he said as little as possible, but of course it could not be entirely hushed up. As Bob was talking, Mr. Taylor took the telephone receiver off the hook and called a number.

By the time his story was finished, a knock sounded on the door and it opened to let in Jenkins, the camp marshal.

“I just telephoned the marshal to come up as we were talking,” explained Mr. Taylor. “I want him to get those two cowboys if he can.”

“Won’t be much chance,” put in Bob, “if they’ve been to the hut. But if they were going to leave me there without food or water, perhaps you can get ’em.”

The engineer stated the case briefly so that the officer would understand.

“I’ll try to git ’em,” announced Jenkins. “I guess I better git the sheriff down to Las Cruces to call out a posse—”“No, don’t do that,” put in Taylor. “This is a Federal job and we don’t want the county in on it. Go to it alone.”

Stolidly the man took his orders and stumped out. When he was gone Mr. Whitney’s assistant turned to Bob.

“What do you think will be the first move? Did you hear anything definite?”

“No, sir, and I haven’t any idea what they’ll do. Anything is likely to happen!”

“Then the only thing to do is to put on extra watchmen and keep a sharp lookout for trouble among the Mexicans. I’ll see to it at once.” He started up as if to go out. Then, remembering Bob, he said, “You’ve done good work, Hazard. Sorry I was so grumpy when you came in. Take the remainder of the day off and rest up.”

“Thank you, sir,” the boy answered, “but I couldn’t sleep now. There’s too much excitement around!”

With this they left the office, Taylor to see that all preparations were made to forestall any attack, and Bob to take up the work Mr. Whitney had left for him to do.The day and night passed quietly, but the next morning the mess room of the Quarter-house was in a turmoil. News had come in that a gang of Mexican bandits had made a raid on Columbus, killing and wounding many Americans. This report was unconfirmed but rumors flew thick and fast. Some had it that it was the army of Carranza and others that it was merely an unorganized deed of a rash bandit. Most of the men thought it was Villa.

When Bob heard the news he immediately connected Mr. Whitney’s prolonged absence with it. The Chief was not back and in all probability he had remained to talk over the best manner of protecting Government property from any mishap. The raid was so daring that it showed the possibility that others might follow and the dam was near enough the border to be in actual danger. Bob realized that in all probability this was just what the cattlemen wanted; that it might mean intervention. Especially so if more outrages took place at once.

All during the day he worked with a cloud of apprehension hanging over him. But nothing stirred. The Mexicans at the noon hour broke up into groups and talked excitedly, but as far as Bob could see they did their work without any friction with their bosses, and under Mr. Taylor’s generalship the whole job moved smoothly.

But there was something wrong in the air. The very calm itself seemed unhealthy, and Bob was glad when nighttime came. He noticed that Mr. Taylor had again put on the extra force of watchmen, as he had planned, all of whom were Americans. This had been done quietly and passed without comment from the Mexicans.

However, just before the quitting whistle blew, Bob happened to be near the spot where the Indians were excavating. He took this opportunity to go up to Feather-in-the-Wind who was directing his men. Ostensibly he asked something regarding the work but it was only to give the Indian a chance to convey any message he might have. The Apache did have something to say.

“Meet Feather-in-the-Wind by rock crusher to-night,” he whispered swiftly, but cautiously.

It was sufficient. Bob walked off unconcernedly but as soon as dark had fallen he went to the appointed place. He had not been there long when the Indian glided up to him.

“Have you learned anything?” asked Bob quickly.

“Yes; Greasers much excited. One man make bad medicine. He Miguel. They plan big strike—no more work. To-day came news much killing on border. Miguel tell ’em Gringo all scared. They keep quiet, then capture dam.”

“Are they going to do what he says?” put in Bob in a tense whisper.

“Yes, Miguel very much strong. Greasers grumble but do what he say.”

But when Bob started to thank Feather-in-the-Wind for finding out what he had, the Apache stopped him. “Wait! More!” he said. “One my young men got keen eyes. Not dimmed by white man’s whiskey. He see Miguel go away from camp one, two, t’ree nights. He take something with him. Young man no follow. No worry him much. Perhaps go to-night. You want us follow?”“You’re whistling,” said Bob shortly.

Probably Feather-in-the-Wind did not understand the slang but he got what Bob meant, for he said, “Come!” and started off in the direction of the lower camp. He did not go through the village but cut up on the hillside, walking swiftly as if he knew where he was bound. Bob followed.

A few minutes later a slim shadow rose out of the chaparral. Feather-in-the-Wind spoke in his own language to this newcomer. Evidently this was the brave who had kept note of Miguel’s comings and goings. The conference over, Bob’s friend uttered the one word, “Wait!” and sat down. The other Indian slipped away. Bob followed the example of Feather-in-the-Wind.

From where they were sitting, screened by the undergrowth, they could see a section of a rough path that led up the hillside. For a long time nothing happened. As the Indian did not speak, Bob felt it best to remain quiet also. Probably there was a reason for it. The delay did not worry him much, however, as there was plenty of material for his mind to be busy with. Ever since he had talked with Mr. Whitney, events had tumbled upon him one after another. Mr. Whitney had gone and Ted was doing outpost duty. Jerry was on the other side. Only the Indian was left to him and he was not much of a counselor. True, he was beginning to prove himself a great help but through the limitations of language he could not be used to discuss what ought to be done regarding the things they found out. What the outcome of the mess was to be was beyond Bob’s imagination to foresee. He was determined to do what he felt was his duty, and if the consequences were serious it could not be helped.

His reverie was broken by a nudge on the arm. He looked up to see a shadow darting along the path. Nearer and nearer it came until it passed almost close enough to the point where they were sitting to be touched by Bob’s hand should he thrust it from cover.

The young Indian had been right. It was Miguel. Even in the uncertain light Bob could see that he carried a queer-shaped package under his arm.

A moment or so later the Indian got up and motioned to Bob that it would be safe to follow. They did not take the path but threaded their way amongst the underbrush, the sand deadening their footsteps. So cleverly did the Indian pick his way that hardly a sound was made by their coming in contact with the bushes. Bob had difficulty in keeping up with his guide, yet he did his best and when they reached the crest of the hill he was but a few steps behind.

Once here, the Indian stopped and took an observation. An almost imperceptible grunt escaped him and, turning on his heel, he motioned Bob to follow. It was a surprising move, for the Indian practically retraced the steps they had just taken. Bob was soon to know the reason, however, for halfway down the hill the Indian spoke, not turning his head.

“Fool Greaser! Go all way up hill only to throw people off track. I know where he make for. Come!”

Bob was breathing hard when they finally reached the spot where the Indian decided to stop. It was above the dam proper and on the same side of the river. Again they established a hiding place in the underbrush but this time it was near the edge of the clearing. Below them was a widening of the river where the coffer dam had been built. This was erected to divert the water of the river into the spillway, which left the river bed dry for the construction of the main dam.

“Why do you think he will come here?” asked Bob, amazed at the Indian’s tactics. He didn’t for a moment doubt that Feather-in-the-Wind knew what he was about, yet it surprised him and he wanted an explanation.

“Easy,” said the Indian. “Only two places go when get top of hill. One way lead to station, other way to upper camp. He start direction upper camp. I know he no go there. Therefore he go round and come back to dam. Nearest place him come back.”

It was easy once it was explained, Bob realized, and the words brought a complete faith in his guide’s methods.

Again silence was necessary, for if Miguel was coming it would not be long before his arrival. Come he did and only a few yards from them. Bob held his breath until Miguel passed them and reached the river level. There he put down his package, which Bob noticed he handled with the utmost care. But this did not impress the boy as much as did the next move of the man under observation. Going up to a rock which showed itself above the ground, he knelt and began scooping away the sand from one side of it. After a few moments of this work he evidently found what he had been digging for, because he picked some objects out of the hole he had made and laid them at his side.

Involuntarily Bob gasped. He recognized what it was that Miguel had taken from the hole and what probably was also in the odd-shaped package he had been carrying.

It was dynamite, dynamite stolen probably from the work and brought up and stored here for some evil purpose. Evidently Miguel was preparing to strike the first blow in the plot against the dam.

Bob kept still, feeling that he would soon know what Miguel planned to do with the explosive, for if whatever plan the Mexican had conceived was not to be consummated to-night, it was evident that he would have buried the additional stuff he had brought instead of digging up his cache.

In this he was not mistaken. Miguel produced from around his body a coil of fuse and began joining the sticks of dynamite and placing detonating caps in them. Every muscle in the boy’s body ached to jump from the hiding place and grapple with the man who was arranging such wholesale destruction, but evidently the Indian realized what was going on within him, for he felt a restraining touch on his arm. At once he knew what it meant. The Indian was telling him that it would be foolish to attack the Mexican when he had so much sudden death in his hands. Before they could reach him, no matter how swiftly they acted, the Mexican could throw the dynamite and the damage would be done. There was nothing to do but wait and hope that Miguel would give them an opening when there was more possibility of averting the catastrophe.

The Mexican worked swiftly and at last he had his infernal machine ready. Straightening up, he carried it to the coffer dam and began laying the dynamite sticks at equal intervals along the bank. This dam was constructed of timber backed up by refuse material from the crusher and the excavation. It was neither high nor wide at this time as it only served to divert the ordinary flow of the Rio Grande. It had not been destined to cope with any flood, should one come, as the engineering plan was to get the dam in such shape as to withstand a freshet before the rainy season came on. But the dynamite the Mexican was laying was sufficient to wreck what had been built, and, should the water be released, it would undo thousands of dollars worth of work at the main dam, besides the delay caused by the rebuilding.

It was the first blow in the Mexican campaign and at all hazards it must be stopped. Bob knew this and the Indian at his side knew it. Miguel went farther and farther from them towards the center of the river. They could follow him with their eyes as his movements were clearly outlined in the white moonlight. There was no watchman on the coffer dam. There seemed no reason for one; yet Bob realized that a watchman was needed everywhere with this plot seething.It was a horrible situation, for there seemed to be nothing that could be done. Probably the Mexican was desperate enough to sacrifice his life if he should be detected while laying his mine. He would set off the dynamite if he saw anything to disturb him. Therefore, to attack him openly seemed out of the question.

What was to be done? There seemed no answer. At last an idea came to Bob. “Go quick,” he said to the Indian, “get help! Bring a gun. Perhaps we can shoot him! I’ll stay here and watch. You can go quicker than I. Hurry!”

Feather-in-the-Wind knew it to be the only plan and started off with long running leaps, keeping himself well hidden from the Mexican. There was just a chance that he could get to the camp and back before Miguel could complete his dastardly work.

As soon as the Indian was gone Bob started to carry out a plan of his own. He knew the Indian would not have allowed him to take the chance, so he had been forced to use a stratagem to get Feather-in-the-Wind out of the way.

Kicking off his shoes, he wormed his way on his stomach towards the upper side of the coffer dam. Miguel was working on the lower side and Bob knew that the dam was sufficiently high to keep his actions hidden from the Mexican.

When he reached the edge of the river Bob slipped into the water with as little noise as possible. Keeping close to the dam he found that he could make fair headway by half swimming and half walking along the slanting boards which held the Rio Grande in check. His plan was desperate, yet it was the only one that seemed feasible. Miguel would probably set a rather long fuse, one long enough to allow him to get safely away. “If I can only get there before the fuse has burned to the first stick of dynamite!” gasped Bob to himself.

Panting, struggling, gasping, he fought on. His mind was filled with the horror of what would happen should he be too late. There was no way of telling how far Miguel had gone. The dam that kept him hidden from the Mexican, also hid the Mexican from him. He must—he must go on until he was well past the center of the dam—Miguel would do the job thoroughly if at all. Once there he must go through a fresh ordeal. He must climb out of the water and look over the edge of the dam in order to get his bearings and to find out where the Mexican had lit the fuse. Should he look over at the wrong spot and Miguel see him, it was the end—the end probably of his life and surely the finish of the coffer dam.

At last he passed the sluice gates which marked the center of the dam. A few rods further on he knew he must climb up and look over.

There was no time in which to gather his nerves together. He must act and act at once. So, pulling himself up with as little noise as possible, he peered over. No Miguel was in sight. But a hundred feet down the dam was a tiny thread of white smoke shining gray in the moonlight. With a despairing sob he leaped towards it as fast as his soaked clothes would let him.