"Have they done any damage?" asked Mr. Damon as he stood in the bow of the Red Streak.

Tom did not answer for a moment. His trained eye was looking over the engine.

"They yanked out the high tension wire instead of stopping the motor with the switch," he answered at length, and then, when he had taken a look into the compartment where the gasoline tank was, he added: "And they've ripped out two more of the braces I put in. Why in the world they did that I can't imagine."

"That's evidently what one man had that the others wanted," was Mr. Damon's opinion.

"Probably," agreed Tom. "But what could he or they want with wooden braces?"

That was a puzzler for Mr. Damon, but he answered:

"Perhaps they wanted to damage your boat and those two men were mad because the other got ahead of them."

"Taking out the braces wouldn't do much damage. I can easily put others in. All it would do would be to cause the tank to sag down and maybe cause a leak in the pipe. But that would be a queer thing to do. No, I think there's some mystery that I haven't gotten to the bottom of yet. But I'm going to."

"Good!" exclaimed Mr. Damon. "I'll help you. But can you run your boat back home?"

"Not without fixing it a bit. I must brace up that tank and put in a new high-tension wire from the spark coil. I can do it here, but I'd rather take it to the shop. Besides, with two boats to run back, for I must return Andy's to him, I don't see how I can do it very well unless you operate one, Mr. Damon."

"Excuse me, but I can't do it. Bless my slippers, but I would be sure to run on a rock! The best plan will be for you to tow your boat and I'll ride in it and steer. I can do that much, anyhow. You can ride in the Red Streak."

Tom agreed that this would be a good plan. So, after temporarily bracing up the tank in the Arrow, it was shoved out into the lake and attached to Andy's craft.

"But aren't you going to make a search for those men?" asked Mr. Damon when Tom was ready to start back.

"No, I think it would be useless. They are well away by this time, and I don't fancy chasing them through the woods, especially as night is coming on. Besides, I won't leave these boats."

"No doubt you are right, but I would like to see them punished, and I am curious enough to wish to know what object that scoundrel could have in ripping out the blocks that served as a brace for the tank."

"I feel the same way myself," commented the lad, "especially since this is the second time that's happened. But we'll have to wait, I guess."

A little later the start back was made, Mr. Damon steering the Arrow skillfully enough so that it did not drag on the leading boat, in which Tom rode. His course took him not far from the lake sanitarium, where Mr. Duncan, the hunter, had been brought, and desiring to know how the wounded man was getting on, the youth proposed that they make a halt, explaining to Mr. Damon his reason.

"Yes, and while you're about it you'd better telephone your father that you will join him tomorrow," suggested the other. "I know what it is to fret and worry. You can fix your boat up in time to go to Sandport to-morrow, can't you?"

"Yes, I'm glad you reminded me of it. I'll telephone from the sanitarium, if they'll let me."

Mr. Duncan was not at the institution, Tom was told, his injury having healed sufficiently to allow of his being removed to his home. The youth readily secured permission to use the telephone, and was soon in communication with Mr. Swift. While not telling him all the occurrences that had delayed him, Tom gave his father and Ned Newton enough information to explain his absence. Then the trip to Shopton was resumed in the two boats.

"What are you going to do about your automobile?" asked Tom as they neared the point where the machine had been left.

"Never mind about that," replied Mr. Damon. "It will do it good to have a night's vacation. I will go on to your house with you, and perhaps I can get a train back to my friend's home, so that I can claim my car."

"Won't you stay all night with me?" invited the young inventor. "I'd be glad to have you."

Mr. Damon agreed, and, Tom putting more speed on the Red Streak, was soon opposite his own dock. The Arrow was run in the boathouse and the owner hastily told Mrs. Baggert and the engineer what had occurred. Then he took Andy's boat to Mr. Foger's dock and warmly thanked the red-haired lad for the use of his craft.

"Did you find your boat?" asked Andy eagerly. "How did the Red Streak run?"

"I got my boat and yours runs fine," explained Tom.

"Good! I'll race you again some day," declared Andy.

Mr. Damon enjoyed his visit at our hero's house, for Mrs. Baggert cooked one of her best suppers for him. Tom and the engineer spent the evening repairing the motor-boat, Mr. Damon looking on and exclaiming "Bless my shoe leather" or some other part of his dress or anatomy at every stage of the work. The engineer wanted to know all about the men and their doings, but he could supply no reason for their queer actions regarding the braces under the gasoline tank.

In the morning Tom once more prepared for an early start for Sandport, and Mr. Damon, reconsidering his plans, rode as far with him as the place where the automobile had been left. There he took leave of the young inventor, promising to call on Mr. Swift in the near future.

"I hope you arrive at the hotel where your father is without any more accidents," remarked the automobilist. "Bless my very existence, but you seem to have the most remarkable series of adventures I ever heard of!"

"They are rather odd," admitted Tom. "I don't know that I particularly care for them, either. But, now that I have my boat back, I guess everything will be all right."

But Tom could not look ahead. He was destined to have still more exciting times, as presently will be related.

Without further incident he arrived at the Lakeview Hotel in Sandport that evening and found his father and Ned very glad to see him. Of course he had to explain everything then, and, with his son safely in his sight, Mr. Swift was not so nervous over the recital as he would have been had Tom not been present.

"Now for some nice, quiet trips," remarked the lad when he had finished his account. "I feel as if I had cheated you out of part of your vacation, Ned, staying away as long as I did."

"Well, of course we missed you," answered his chum. "But your father and I had a good time."

"Yes, and I invented a new attachment for a kitchen boiler," added Mr. Swift. "I had a chance for it when I passed through the hotel kitchen one day, for I wanted to see what kind of a range they used."

"I guess there's no stopping you from inventing," replied his son with a laugh and a hopeless shake of the head. "But don't let it happen again when you go away to rest."

"Oh, I only just thought of it," said Mr. Swift. "I haven't worked the details out yet."

Then he wanted to know about everything at home and he seemed particularly anxious lest the Happy Harry gang do some damage.

"I don't believe they will," Tom assured him. "Garret and Mrs. Baggert will be on guard."

The next few days were pleasant ones for Tom, his father and Ned Newton. They cruised about the lake, went fishing and camped in the woods. Even Mr. Swift spent one night in the tent and said he liked it very much. For a week the three led an ideal existence, going about as they pleased, Ned taking a number of photographs with his new camera. The Arrow proved herself a fine boat, and Tom and Ned, when Mr. Swift did not accompany them, explored the seldom visited parts of Lake Carlopa.

The three had been out one day and were discussing the necessity of returning home soon when Ned spoke.

"I shall hate to give up this life and go to slaving in the bank again," he complained. "I wish I was an inventor."

"Oh, we inventors don't have such an easy time," said Mr. Swift. "You never know when trouble is coming," and he little imagined how near the truth he was.

A little later they were at the hotel dock. When Tom had tied up his boat the three walked up the path to the broad veranda that faced the lake. A boy in uniform met them.

"Some one has just called you on the telephone, Mr. Swift," he reported.

"Some one wants me? Who is it?"

"I think he said his name is Jackson, sir, Garret Jackson, and he says the message is very important."

"Tom, something has happened at home!" exclaimed the inventor as he hurried up the steps. "I'm afraid there's bad news."

Unable to still the fear in his heart, Tom followed his father.