So unexpected was his encounter with Andy that the young inventor hardly knew how to act, especially since he was a guest of the young ladies. Tom did not want to do or say anything to embarrass them or make a scene, yet he did want to have a talk, and a very serious talk, with Andy Foger.

Miss Nestor must have noticed Tom's sudden start at his glimpse of Andy, for she asked: "Did you see some one you knew, Mr. Swift?"

"Yes," replied Tom, "I did---er---that is---" He paused in some confusion.

"Perhaps you'd like----that is prefer---to go with them instead of taking lunch with girls who don't know anything about engines?" she persisted.

"Oh, no indeed," Tom hastened to assure her. "He---that is---the person I saw wouldn't care to have me lunch with him," and the youth smiled grimly.

"Would you like to bring him over to our table?" inquired Miss Carson. "We have plenty for him."

"No, I think that would hardly do," continued the lad, who tried not to smile at the picture of the red-haired and squint-eyed Andy Foger making one of a party with the girls. The young ladies fortunately had not noticed the bully, who was out of view by this time.

Tom was presented to Mr. and Mrs. Nestor, who told him how glad they were to meet the young man who had been instrumental in saving their daughter from injury, if not death. Tom was a bit embarrassed, but bore the praise as well as he could, and he was very glad when a diversion, in the shape of lunch, occurred.

After a meal on tables under the trees in the grove Tom took the girls and some of their friends out in his motor-boat again. They covered several miles around the lake before returning to the picnic ground.

As Tom was starting toward home in his boat, wondering what had become of Andy and trying to think of a reason why the bully should attend anything as "tame" as a church picnic, the object of his thoughts came strolling through the trees down to the shore of the lake. The moment he saw Tom the red-haired lad started back, but the young inventor, leaping out of his boat, called out:

"Hold on there, Andy Foger, I want to see you!" and there was menace in Tom's tone.

"But, I don't want to see you!" retorted the other sulkily. "I've got no use for you."

"No more have I for you," was Tom's quick reply. "But I want to return you these keys. You dropped them in my boat the other night when you tried to set it afire. If I ever catch you---"

"My keys! Your boat! On fire!" gasped Andy, so plainly astonished that Tom knew his surprise was genuine.

"Yes, your keys. You were a little, too quick for me or I'd have caught you at it. The next time you pick a lock don't leave your keys behind you," and he held out the jingling ring.

Andy Foger advanced slowly. He took the bunch of keys and looked at the tag.

"They are mine," he said slowly, as if there was some doubt about it.

"Of course they are," declared Tom. "I found them where you dropped them---in my boat."

"Do you mean over at the auction?"

"No, I mean down in my boathouse, where you sneaked in the other night and tried to do some damage.

"The other night!" cried Andy. "I never was near your boathouse any night and I never lost my keys there! I lost these the day of the auction, on Mr. Hastings' ground, and I've been looking for them ever since."

"Didn't you sneak in my boathouse the other night and try to do some mischief? Didn't you drop them then?"

"No, I didn't," retorted Andy earnestly. "I lost those keys at the auction, and I can prove it to you. Look, I advertised for them in the weekly Gazette."

The red-haired lad pulled a crumpled paper from his pocket and showed Tom an advertisement offering a reward of two dollars for a bunch of keys on a ring, supposed to have been lost at the auction on Mr. Hastings' grounds in Lanton. The finder was to return them to Andy Foger.

"Does that look as if I lost the keys in your boathouse?" demanded the bully sneeringly. "I wouldn't have advertised them that way if I' been trying to keep my visit quiet. Besides, I can prove that I was out of town several nights. I' was over to an entertainment in Mansburg one night and I didn't get home until two o'clock in the morning, because my machine broke down. Ask Ned Newton. He saw me at the entertainment.

Andy's manner was so earnest that Tom could not help believing him. Then there was the evidence of the advertisement. Clearly the squint-eyed youth had not been the mysterious visitor to the boathouse and had not unlocked the forward compartment. But if it was not he, who could it have been and how did the keys get there? These were questions which racked Tom's brain.

"You can ask Ned Newton," repeated Andy. "He'll prove that I couldn't have been near your place, if you don't believe me."

"Oh, I believe you all right," answered Tom, for there could be no doubting Andy's manner, even though he and the young inventor were not on good terms. "But how did your keys get in my boat?"

"I don't know, unless you found them, kept them and dropped them there," was the insolent answer.

"You know better than that," exclaimed Tom.

"Well, I owe you a reward of two dollars for giving them back to me," continued the bully patronizingly. "Here it is," and he hauled out some bills.

"I don't want your money!" fired back Tom.

"But I'd like to know who it was that was in my boat."

"And I'd like to know who it was took my keys," and Andy stuffed the money back in his pocket. Tom did not answer. He was puzzling over a queer matter and he wanted to be alone and think. He turned aside from the red-haired lad and walked toward his motor-boat

"I'll give you a surprise in a few days," Andy called after him, but Tom did not turn his head nor did he inquire what the surprise might be.

Mr. Swift was somewhat puzzled when his son related the outcome of the key incident. He agreed with Tom that some one might have found the ring and kept it, and that the same person might have been the one whom Tom had surprised in the boathouse.

"But it's idle to speculate on it," commented the inventor. "Andy might have induced some of his chums to act for him in harming your boat, and the key advertisement might have been only a ruse."

"I hardly think so," answered his son, shaking his head. "It strikes me as being very curious, and I'm going to see if I can't get at the bottom of it."

But a week or more passed and Tom had no clew. In the meanwhile he was working away at his motor-boat, installing several improvements.

One of these was a better pump, which circulated the water around the cylinders, and another was a new system of lubrication under forced feed.

"This ought to give me a little more speed," reasoned Tom, who was not yet satisfied with his craft. "Guess I'll take it out for a spin."

He was alone in the Arrow, taking a long course up the lake when, as he passed a wooded point that concealed from view a sort of bay, he heard the puffing of another motor-boat.

"Maybe that's Mr. Hastings," thought Tom. "If I raced with him now, I think the Arrow could give a better account of herself.

The young inventor looked at the boat as it came into view. It needed but a glance to show that it was not the Carlopa. Then, as it came nearer, Tom saw a familiar figure in it---a red-haired, squint-eyed chap.

"Andy Foger!" exclaimed Tom. "He's got a motor-boat! This is the surprise he spoke of."

The boat was rapidly approaching him, and he saw that it was painted a vivid red. Then he could make out the name on the bow, Red Streak. Andy was sending the craft toward him at a fast rate.

"You needn't think you're the only one on this lake who has a gasoline boat!" called Andy boastfully. "This is my new one and the fastest thing afloat around here. I can go all around you. Do you want to race?"

It was a "dare," and Tom never took such things when he could reasonably enter a contest. He swung his boat around so as to shoot alongside of Andy and answered:

"Yes, I'll race you. Where to?"

"Down opposite Kolb's dock and back to this point," was the answer. "I'll give you a start, as my engine has three cylinders. This is a racing boat."

"I don't need any start," declared Tom. "I'll race you on even terms. Go ahead!"

Both lads adjusted their timers to get more speed. The water began to curl away from the sharp prows, the motors exploded faster and faster. The race was on between the Arrow and the Red Streak.