"What's the matter?" Charley asked the engineer. "You can see for yourself," was the reply. "Look at that little brook over there where we have been getting our water. Last night it was just ordinary sweet, pure, cold water, but just look at it now." The two lads stepped over to the tiny brook McCarty pointed out. It was only a few feet wide and three or four inches in depth, except where the machine men had dug a hole a couple of feet deep to make possible the dipping up of a few bucketfuls at a time. The boy's eyes opened wide with wonder and surprise, for the waters of the little rill were red like blood. "Queer, isn't it?" said McCarty. "Hanged if I can account for it." "I have seen brooks of that color where the water flowed over red bay tree roots," Walter volunteered. "That color does not come from bay roots," objected the other. "You want to remember that it was all right and colorless yesterday. We got a fresh pail of water about two hours ago. Of course we did not notice the color then because it was dark, but one of the men went to get a drink a while ago and I thought he would throw a fit when he saw the color of the stuff he had been drinking. Bossie washed his face and hands in the brook a couple of hours ago and just look at him now." The lads glanced at the Spaniard, whose frightened face was a bright red. "They want to quit," McCarty continued in a low voice. "This, coming after all the other mystery, has scared them out of their wits. Unless you can hit upon some reasonable explanation of this thing and do it quick, I am afraid the whole gang will quit. They have been crossing themselves and muttering prayers to the Virgin for the last hour." A glance at the three frightened Spaniards convinced the two lads that McCarty was not exaggerating the seriousness of the situation. "Keep them here until I come back," Charley told him softly. "Come on, Walt, I am going to follow that rill up to its source." They had not far to go. A couple of hundred yards from the machine they found the rill's source among a clump of willows. Here a little spring bubbled up from the ground. Near its mouth, fastened tightly to a stake, was an object that caused the boy to utter exclamations of surprise and relief. It was a muslin bag capable of holding eight or ten pounds and it was stained a bright red. It had been cunningly placed in a narrow part of the rill and the dirt banked up on both sides so that all the water from the spring would have to pass through or over it. "Don't touch it," Charley said. "Go bring the machine men here. I want to make this an object lesson to them." While Walter was gone on this errand, the lad gathered up several pasteboard packages that lay scattered around on the ground. He noted with satisfaction that the directions on them were printed in Spanish as well as English.