“Nothing but the wind,” murmured George, as a shutter rattled. “Hark!” ordered Tom again. There was some sound outside. All the boys heard it plainly, and a dog they had borrowed that day from Sam, to help them in tracking any game on the trail of which they might get, sat up and growled. “Someone is out there,” said Tom in a whisper. “Some animal--a skunk, maybe,” suggested Bert. “I’m going to stay in. I don’t like him--not for a scent!” and he laughed at his own joke. Tom, however, was softly getting up from the couch. He looked fixedly toward one certain window. “Jack, turn the light out suddenly!” he ordered in a whisper. “Bert, have your gun ready.” “Do you really think it is--anyone?” asked Bert, as he reached for his gun, which he had finished cleaning, and put together again. “Someone or--something,” went on Tom, and his voice did not rise above a whisper. He moved slowly over toward the window. “Here goes the glim!” Jack announced, and at once the cabin was darkened. It took but a minute, however, for the boys’ eyes to become accustomed to the change, and they saw moonlight streaming through the window toward which Tom was moving. The others followed him, walking softly. “There he goes--it _is_ someone!” hoarsely whispered Bert, and he pointed to a black figure stealing over the snow. It was plainly in sight, for the ground was deeply covered with snow. “It’s a bear!” George burst out. “It’s a bear! Where’s my gun? Where do you shoot a bear, anyhow? I don’t want to spoil the skin. Say, where’s my gun?” “Dry up!” ordered Tom sharply. “It isn’t a bear!” “It is so!” began George. “Where’s my----” Before anyone could stop him, or object, Bert had slipped to the door, opened it, and had fired his gun at the retreating black object. “Look out!” Tom cried. “You might kill him! That’s a man--not a bear, Bert!” “I know it,” was the calm answer. “I only fired over his head to scare him. Look at him scoot, would you?” And indeed the black object that George had thought was a bear suddenly straightened up, revealing itself to be a man. He ran with fast strides toward the circle of woods that were all about the hunting cabin. The man reached the shelter of the black trees a little later, and was soon lost to sight. “A man!” gasped George. “It was a man!” “That’s what it was,” added Bert. “Well, what do you know about that?” demanded Jack. “Was he sneaking around this cabin?” “That’s about it,” answered Tom. “But who was he?” “That’s for us to guess,” went on the young hunter. “But I fancy I can come pretty near it.” “You mean Professor Skeel?” asked Bert. “Him, or one of his two friends.” “But what would he, or they, be doing around our cabin?” “That,” said Tom, and he spoke more soberly than he had for some time, “that is something I’d give a great deal to learn. It’s a mystery that’s been bothering me for some time.” The chums looked at their friend in silence for a moment, and then Jack remarked: