Ragged heaps of native rock lay along the foot of the dam, flanking the edge of the great eddy eastward of the apron. Here often the laborers stood and cast their lines for the leaping trout, which, wearied by their fruitless fight at the apron, that carried them only up to the insurmountable obstacle which reached a hundred feet above them, sometimes were swept back to seek relief in the gentler waters of the deep eddy, that swung inshore from the lower end of the apron. Sim Gage saw all these scenes, so familiar by this time, as they lay half revealed under the blaze of the great searchlight. It all seemed safe now, as it always had before. But when at length he turned back to ascend to the upper level, he saw something which caused him to stop for just an instant, and then to spring into action. The power plant proper of the dam was not yet wholly installed, only the dam and turbine-ways being completed. In the power house itself, a sturdy building of rock which caught hold of the immemorial mountain foot beneath it, only a single unit of the dynamos had been installed. This unit had been hooked on, as the engineers phrased it, in order to furnish electric light to the camp itself, for the telephone service of the valley and for the minor machinery which was operated by this or that machine shop along the side of the mountain. A cable from the power house ran up to another house known as the lighting plant, which stood in the angle between the street level and the dam itself. Here was installed a giant searchlight which could be played at will along the face of the dam, to make its examination the more easy and exact by night. The steady stream of this light was a fixed factor, being held at such a position as would cover the greatest amount of the dam face. Now, as Sim Gage topped the grade, gravel crunching under his feet, a trifle out of breath with his climb, since the incline itself was a thing of magnificent distances, he saw the searchlight of the power dam begin a performance altogether new in his own experience. The great shaft of light rose up abruptly to a position vertical, a beam of light reaching up into the sky. An instant, and it began to swing from side to side. It swung sharply clear against the bald face of the mountain at the farther end of the dam. It swept down the canyon itself, or to its first great bend. It rose again and swept across the dark-fringed summit of the mountains on the hither side of the stream. Not once, but twice, this was done. It was a splendid and magnificent thing itself, this giant eye, illuminating and revealing, fit factor in a wild and imposing panorama of the night. But why? No one ever had known the searchlight to be used in this way. What orders had been given? What did these zig-zag beams up and down the surface of the sky indicate? Was it a signal, or was some one playing with the property of the Company, there in the cupola of the light station?