Gillow was glad to obey, for, though there was faint moonlight, he had already cut one knee cruelly. It was bitterly cold beneath the boulder where he crouched in the snow, and when the black object, which worked its way along the bending cable, had disappeared in the gloom of overhanging rocks on the opposite shore, there was nothing to see but the tossing spray of the river. The stream was still a formidable torrent, though now that the feeding snows were frozen fast, it was shrunken far below its summer level. A good many minutes had passed with painful slowness when Gillow, who regretted that he had left the snug cook-shed, said:
"This is distinctly monotonous, and it's about time we struck back to camp. Guess that fellow has tackled too much Red Pine whiskey, and is just walking round to cool himself."
In answer the foreman grasped the speaker's shoulder, and stretched out a pointing hand. The moonlight touched one angle of the rock upon the opposite shore which encroached upon the frothing water, and the dark figure showed sharply against it. The figure vanished, reappeared, and sank from sight again. When this had happened several times Gillow remarked: "Perhaps we had better go over. The man's clean gone mad."
"No, sir!" objected Mattawa Tom. "No more mad than you. See what he's after? No! You don't remember, either, how mighty hard it was to wedge in the holdfasts for the chain guys stiffening the front of the dam, or how the keys work loose? There wouldn't be much of the boring machines or dam framing left if the chains pulled those wedges out. Catch on to the idee?"
Gillow gasped. The huge timber framing, which held back the river so that the costly boring machines could work upon the reef, cumbering part of its bed, had been built only with the greatest difficulty, and when finished Thurston had found it necessary to strengthen it by heavy chains made fast in the rock above. The sockets to which these were secured had been wedged into deep-sunk holes, but more than once some of the hard wood keys had worked loose, and Gillow could guess what would happen if many were partially set free at the same time.
"If he hammered three or four of those wedges clear it would only need a bang on another one to give the river its way," Gillow said excitedly. "Then it would take Thurston six months to fix up the damage, if he ever did, and nobody would know how it happened. The cold-blooded brute's in the maintenance gang?"
"Just so. A blame smart man, too!" asserted Mattawa Tom. "I guess the boss wouldn't want everybody to know. Rustle back your hardest and bring him along."
Fifteen minutes later Thurston took his place behind the boulder, and, because the light was clearer now, he could dimly see the man swinging a heavy hammer, against the rock. He knew that the miscreant, whose business was to prevent the possibility of such accidents, need only start a few more keys, which he would probably do when the dam was clear of men, and many thousand dollars' worth of property and the result of months of labor would be swallowed by the river. His face paled with fierce anger when he recognized this fact.
"I want that man," he declared with shut teeth. "I want him so badly that I'd forfeit five hundred dollars sooner than miss him. Slip forward, Gillow, as much out of sight as you can, and hide yourself on the other side of the ladder. Mattawa and I will wait for him here, and among us three we ought to make sure of him."
Gillow, who stole forward stooping, swore softly as he fell over many obstacles on the way. The man they wanted became visible, ascending another ladder across the river. Then, hanging in the suspended trolley, he moved, a black shape clear against the snow—along the wire which stretched high across the gulf. While the others watched him, his progress grew slower on reaching the hollow, where the cable bent slightly under the weight at its center. Suddenly the car's progress was checked altogether, and it began to move in the opposite direction more rapidly than before, while Thurston sprang to his feet.