The success of their enterprise was dependent upon one of these sentries being put out of action for some minutes. This was no easy matter, but by dint of much discussion and careful observation they reached the conclusion that it could be done; and, better still, done so that no alarm need be given. A Sunday night was fixed for the attempt, because Max and Dale had never worked on Sundays, and their absence would not therefore be likely to arouse any subsequent suspicion that they had had anything to do with the matter. Moreover, all departments of the works were run on reduced staffs, and the staff of the power-house was reduced proportionately. The loss of life which both Max and Dale feared might ensue from the realization of their plans was thus brought to a minimum. Shortly after midnight, Max, Dale, and Dubec made their way silently to the little cache of shells in the river bank, and began transporting them to a point as near the power-house as they could expect to get without attracting notice. There was a bright moon, but there were also clouds, and they patiently bided their time, and moved only when the moon was obscured. It was one o'clock before the whole of the shells had been transported within easy reach of the power-house. The sentries were changed at two o'clock, and Max and Dale waited only until this had been completed. Then they drew near, and took a long look at the sentry upon the least-exposed corner of the building. He was a young fellow, and while not looking particularly alert, yet seemed fully alive to his duties and determined to carry them out. As has already been explained, he was posted at a corner of the building, and could command a view of two sides. One of these sides was flooded with the light of the moon, but the other was in shadow, except at intervals where it was cut by the light from the windows of the power-house, which were here on a level with the ground. After a whispered word or two, Dale left Max and worked his way round until he was near the side of the building which was in shadow. Watching his chance, he slipped into the shadow at a moment when the sentry was gazing the other way. Max now retreated some distance, and then began boldly advancing towards the building, his feet crunching heavily into the gravel and giving the sentry every warning of his approach. The sentry watched him with lazy indifference, but, as he drew near, lifted rifle and bayonet and challenged. "Who comes there?" "A workman with message to the engineer," responded Max in a casual voice, slackening his pace and coming to a stop a few paces away. "Pass," replied the sentry indifferently, letting the butt of his rifle drop again to the ground. Max slouched on again, directing his steps so that he would pass just in front of the young soldier.