It was still raining, that cold rain which at times turns for a moment or two to snow, and it dashed in gusts against the window panes. Harry was with some of the younger people in the library, where they were playing at games. The sport lagged presently and he went to a window, where he stood between the curtain and the glass. He saw the outside dimly, the drenched lawn, and the trees beyond, under which two or three sentinels, wrapped closely in heavy coats, walked to and fro. He gazed at them idly, and then a shadow passed between him and them. He thought at first that it was a blurring of the glass by some stronger gust of rain, but the next moment his experience told him that it could not be so. He had seen a shadow, and the shadow was that of a man, sliding along against the wall of the house, in order that he might not be seen by a sentinel. Harry's suspicions were up and alive in an instant. In this border country spies were numerous. It was easy to be a spy where people looked alike and spoke the same language with the same accent. His suspicions, too, centered at once upon Shepard, whom he knew to be so daring and skillful. The lad was prompt to act. He slipped unnoticed into the hall, put on his greatcoat, felt of the pistol in his belt, opened the front door and stepped out into the dark and the rain. CHAPTER V. THE NORTHERN ADVANCE Harry flattened himself against the wall and all his training and inherited instincts came promptly to his service. He knew that he, too, would be in the shadow there, where it was not likely that the sentinels could see him owing to the darkness of the night. Then he moved cautiously toward the window where he had seen the outline. The cold rain beat on his face and he saw the figures of the sentinels moving back and forth, but, black against the black wall, he was confident that he could not be seen by them. Half way to the window, his eyes now having gotten used to the darkness, he knelt down and examined the earth, made soft by the rains. He distinctly saw footprints, undoubtedly those of a man, leading by the edge of the wall, and now he knew that he had not been mistaken. Harry came to the window himself, and, glancing in, he saw that the merriment was going on unabated. He continued his search, following the revealing foot prints. He went nearly all the way around the house and then lost them among heavy shrubbery. He surmised that at this point the spy--he was sure that it was a spy and sure, too, that it was Shepard--had left the place, passing between the sentinels in the rainy dark. He spoke to the sentinels, who knew him well, and they were quite confident that nobody had come within their lines. But Harry, while keeping his own counsel, held another opinion and he was equally positive about it. He was returning to the house, when he heard the tread of hoofs, and then a horseman spoke with the sentinels. He looked back and recognized Sherburne.