Tom Swift saw the craft almost as soon as did his chum. It was rather a large-sized motor boat, quite some distance out from shore, and there was no other craft near it at this time. From the quick, first view Tom and Ned had of it, they decided that a party of excursionists were on a pleasure trip.

But that an accident had happened, and that trouble, if not, indeed, danger, was imminent, was at once apparent to the young inventor and the other occupant of the swiftly moving airship.

For as Tom shut off his motor, to volplane down, thus reducing all noise on his craft, they could dimly hear the shouts and calls for help, coming from the water craft below them.

"Help! Help!" came the impassioned appeals, floating up to Tom and Ned.

"We're coming!" Tom answered, though it is doubtful if his voice was heard. Sound does not seem to carry downward as well as upward, and though Tom's craft was making scarcely any noise, save that caused by the rush of wind through the struts and wires, there was so much confusion on the motor boat, to say nothing of the engine which was going, that Tom's encouraging call must have been unheard.

"What are you going to do, Tom?" asked Ned, "You can't land on the water!"

"I know it; worse luck! If I only had the hydroplane, now, we could make a thrilling rescue--land right beside the other boat and take 'em all off. But, as it is, I'll have to land as near as I can and then we will look for a boat to go out to them in."

Ned saw, now, what Tom's object was. On one shore of the lake was a large, level field, suitable for a landing place for the craft of the air. At least it looked to be a suitable place, but Tom would be obliged to take a chance on that. This field sloped down to the beach of the lake, and as Ned and his chum came nearer to earth they could see several boats on shore, though no persons were near them. Had there been, probably they would have gone to the rescue.

Tom cast a rapid look across the sheet of water, to make sure his services were really needed. The motor boat was lower in the lake now, and was, undoubtedly, sinking. And no other craft was near enough to render help. Though distant whistles, seeming to come from approaching craft, told of help on the way.

"Hold fast, Ned!" cried Tom, as they neared the earth. "We may bump!"

But Tom Swift was too skillful a pilot to cause his craft to sustain much of a crash. He made an almost perfect "three point landing," and there would have been no unusual shaking, except for the fact that the field was a bit bumpy, and the craft more heavily laden than usual.

"Good work, Tom!" cried Ned, as the Lucifer slackened her speed, the young inventor having sent her around in a half circle so that she now faced the lake. Then Tom and Ned climbed from the cockpit, throwing off goggles and helmets as they ran to the shore where there were several rowboats moored.

"And a little old-fashioned naphtha launch! By all that's lucky!" cried Tom. "I didn't think they made these any more. If she only works now!"

There was a little dock at this point on the lake, and the boats appeared to be held at it for hire. But no one was in charge, and Tom and Ned made free with what they found. They considered they had this right in the emergency.

The naphtha launch was chained and padlocked to the dock, but using an oar Tom burst the chain.

"Get one of the rowboats and fasten it to the back of the launch!" Tom directed Ned. "I don't believe this craft will hold them all," and he nodded toward those aboard the sinking boat -- for it was only too plainly sinking now.

"All right!" voiced Ned. "I'm with you. Can you get that engine to work?"

"She's humming now," announced Tom, as he turned on the naphtha, and threw in a blazing match to ignite it, this act saving his hand. Naphtha engines are a trifle treacherous.

A few moments later, though not as quickly as a gasoline craft could have been gotten under way, Tom was steering the small launch out and away from the dock, and toward the craft whence came the faint calls for help. Behind them Tom and Ned towed a large rowboat.

Tom speeded the naphtha craft to its limit, and, fortunately for those in danger, it was a fast boat. In less time than they had thought possible, the young inventor and his chum were near the boat that was now low in the water--so low, in fact, that her rail was all but awash.

"Oh, take us out! Save us!" screamed some of the girls.

"Take it easy now," advised Tom, approaching with care. "We've got room for you all. Ned, get back in the rowboat and bring that alongside--on the other side. We'll take you all in," he added.

"Girls first!" called Ned sternly, as he saw one young fellow about to scramble into the naphtha boat.

"Sure, girls first!" agreed the skipper of the disabled craft. "Hit a submerged log," he explained to Tom, as the work of rescue proceeded. "Stove a hole in the bow, but we stuffed coats and things in, and made it a slow leak. Kept the engine going as long as we could, but I thought no one would ever come! Lucky you happened to see us from up there!"

"Yes," assented Tom shortly. He and Ned were too busy to talk much, as they were aiding in getting some hysterical girls and young women into the two sound craft. And when the last of the picnic party had been taken off, the boat with a hole in it gave a sudden lurch, there was a gurgling, bubbling sound, and she sank quickly.

Tom and Ned had anticipated this, however, and had their craft well out of the way of the suction.

"You'll all have to sit quiet," Tom warned his passengers as he took Ned's boat, with her load, in tow. "I've got about all the law allows me to carry," he added grimly.

"Oh, what ever would we have done without you?" half sobbed one girl.

"I guess you could have managed to swim ashore," Tom answered, not wanting to make too much of his effort.

Then more rescue boats came up, but those in the naphtha craft, and Ned's smaller one, refused to be transferred, and remained with our friends until safely landed at the dock.

Receiving the half-hysterical thanks of the party, and leaving them to explain matters to the owner of the borrowed boats, Ned and Tom went back to the Lucifer, and were soon aloft again.

"Pretty slick act, Tom," remarked Ned.

"Oh, it's all in the day's work," was the answer. He had all but perfected his big fire-extinguishing aeroplane, and was contemplating means by which he could give a demonstration to the fire department of some big city, when Mr. Baxter asked to see Tom one day. There was a look on the face of the chemist that caused Tom to exclaim with a good deal of concern:

"What's the matter?"

"Only the same old trouble," was the discouraged answer. "I can't get on the track of my lost secret formulae. If I had Field and Melling here now I--I'd--"

He did not finish his threat, but the look on his face was enough to show his righteous anger.

"I wish we could do something to those fellows!" exclaimed Tom energetically. "If we only had some direct evidence against them!"

"I've got evidence enough--in my own mind!" declared Mr. Baxter.

"Unfortunately that doesn't do in law," returned Tom. "But now that I have this airship firefighter craft so nearly finished, I can devote more time to your troubles, Mr. Baxter."

"Oh, I don't want you bothered over my troubles," said the chemist. "You have enough of your own. But I'm at my wit's end what to do next."

"If it is money matters," began Tom.

"It's partly that, yes," said the other, in a low voice. "If I had those dye formulae, I'd be a rich man."

"Well, let me help you temporarily," begged Tom. And the upshot of the talk was that he engaged Mr. Baxter to do certain research work in the Swift laboratories until such time as the chemist could perfect certain other inventions on which he was working.

In return for his kindness to a fellow laborer, Tom received from Mr. Baxter some valuable hints about fire-extinguishing chemicals, one hint, alone, serving to bring about a curious situation.

It was several days after the accident to the motor boat from which the young inventor and Ned Newton had rescued the party of pleasure seekers that Tom was visited by Mr. Damon, who drove over in his car.

"Have you anything special to do, Tom?" asked the eccentric man. "If you haven't I wish you'd take a ride with me. Not for mere pleasure! Bless my excursion ticket, don't think that, Tom!" cried his friend quickly.

"I know better than to ask you out for a pleasure jaunt. But I have become interested in a certain candy-making machine that a man over in Newmarket is anxious to sell me a share in, and I'd like to get your opinion. Can you run over?"

"Yes," Tom answered. "As it happens I am going to Newmarket myself."

"Oh, I forgot about Mary Nestor being there!" laughed Mr. Damon. "Sly dog, Tom! Sly dog!" and he nudged the youth in the ribs.

"It isn't altogether Mary. Though I am going to see her," Tom admitted. "It has to do with a little apparatus I am getting up. I can capture several birds in the same auto, so I'll go along."

This pleased Mr. Damon, and he and Tom were soon speeding over the road. It was just outside Newmarket that they saw an automobile stalled at the foot of a hill which they topped. It needed but a glance to show that there was serious trouble. As Mr. Damon's car went down the slope two men could be seen leaping from the other machine. And, as they did so, flames burst out of the rear of the stalled machine.

"Fire! Fire!" cried Mr. Damon, rather needlessly it would seem, as any one could see the blaze.

"Another chance!" exclaimed Tom, reaching down between his feet for a wrapped object he had placed in Mr. Damon's car. "It's Field and Melling!" he cried. "The two men who boasted of having put it over on Mr. Baxter. Their car is blazing. Here's where I get a chance to heap coals of fire on their heads!"