"Why, father has even selected him as one of the guards for the factory," said Bob. "I guess that shows how much confidence he has in him." "But suppose Lena is disloyal," exclaimed Hugh. "If Karl Hoffmann is in love with her there's no telling what she might get him to do." "But Lena is not disloyal," said Bob peevishly. He was becoming tired of Hugh's constant slurs against the people whom his father employed. "Well, I'd watch them all," said Hugh. Bob offered no further comment. He could not convince Hugh that his suspicions were unfounded so he decided there could be no use in arguing with him. They entered the house and found Mr. Cook seated in the library alone. "Did you deliver my note?" he asked. "We did," replied Bob. "Who came to the door?" "Frank," and Bob related their experiences to his father. Mr. Cook was much interested and puzzled by the manner in which Frank had acted when he saw the drawing of the alligator on the back of the envelope. "We thought perhaps it might be the sign of some secret society," said Hugh. "Possibly so," agreed Mr. Cook. "Let's see; the same sign was on the paper you found in the old house, Heinrich got a note with the picture on it, and now this letter you picked up on the Wernbergs' porch had it too." "And the handwriting was the same as on that postal card you got this morning," said Bob. "I didn't see any picture on that though." "No," agreed Bob. "Neither did I." "I threw the card away," said Mr. Cook. "I was afraid your mother might find it and worry." "Perhaps there won't be any more trouble, now that Mr. Wernberg is out of the way," suggested Bob. "If he was the leader of the gang, his burns will keep him in the hospital and out of mischief for some time to come." "You didn't hear what happened this afternoon then?" asked his father. "No, what?" demanded Bob and Hugh in one breath. "You remember the railroad bridge, don't you?" "I guess we'll never forget that, will we, Hugh?" exclaimed Bob. "You don't mean that they tried to blow it up again?" "Well, it looks so," said Mr. Cook. "One of the guards on the bridge this afternoon saw a man coming down the river in a rowboat. He called to him to halt, but the man kept right on. The guard challenged him three times, but as the man gave no answer he fired at him." "Did he kill him?" demanded Bob excitedly. "No," said Mr. Cook, "he didn't try to kill him. He just wanted to scare him, and when he fired the man jumped out of the boat into the water. The guard hurried down to the bank of the river, but the man had scrambled ashore and run off; you know it's quite a long distance from where the railroad tracks cross the bridge down to the water. The guard got a long pole and waded out into the river after the boat. He caught it finally and when he had hauled it ashore he found it was loaded with dynamite. Of course no one knows, but they think he planned to blow up the bridge." "Whew!" exclaimed Hugh. "The man got away, you say?"