"They are on their way out West, and I suppose they ran up here to see the sights. I--I wish I could do something to 'em!" added Nat, bitterly. "Maybe you can," answered Tom Shocker, always open for action. "I'll tell you one thing," he continued, in a low tone. "If they had treated me as they treated you, I'd not let them off so easily." "Will you help me, if I--er--try to fix that Dave Porter?" asked Nat. "He started it. I don't care so much about Lawrence." "Sure I'll help you. Anything you say goes," answered Tom Shocker, readily. He thought he saw a chance of getting another dollar or two out of Nat. The two walked behind some bushes and there talked the matter over for several minutes. "Fargo's is the place to go to," said Shocker, presently. "I know we can trust him." "Of course, I don't want to hurt Porter," said Nat, nervously. "I only want to scare him." "Sure, I understand. We'll scare the wits out of him," returned Tom Shocker. "Now, let me see. I have it--we'll catch him on the bridge. His carriage is bound to come that way, to get off Goat Island." Dave and his friends spent the best part of a quarter of an hour around the Three Sisters Islands and then returned to their carriage. "Now we can go to the hotel and have dinner," said Dunston Porter. "And then we can take a local train back to Buffalo." The carriage was just crossing the bridge that connects Goat Island with the city of Niagara Falls when a man stepped up and stopped the turnout. It was Tom Shocker. "Excuse me, but I reckon this is the number, 176," he said. "Is there a young man here named David Porter?" "Yes, I am Dave Porter," answered Dave, and looked at Shocker curiously. The fellow was a total stranger to him. "Got a note for you," went on Shocker, and produced it. It was sealed and marked _Private_ in plain letters. Wondering what the note could contain, Dave opened and read it. His face changed color and he gave a little gasp. "Excuse me, I'll have to--to leave you for a little while," he stammered to the others. "What's the matter?" asked Roger. "I--I can't tell you just now." Dave turned to his uncle. "Where will you get dinner, Uncle Dunston?" "At the International." "All right--I'll be there before long," answered Dave, and sprang to the ground. "But what's up?" cried Phil. He could see that his chum was much disturbed. "I--I can't tell you, Phil. But I'll be back before you finish your dinner." "Don't you want some one along?" asked Laura, who did not like to see her brother depart in the company of such a looking stranger as Tom Shocker. "No, Laura. Oh, it's all right. I'll be at the International on time," said Dave, and then he hurried over the bridge and down a side street of the city, in company with Tom Shocker. The note Dave had received was written in a cramped hand and ran as follows: