Dorothy and Mr. Dixon were finishing breakfast next morning when the Boltons, father and son, dropped in.

“Good morning, stranger,” was Mr. Dixon’s greeting to Bill. “I understand you’ve been to Europe and back a couple of times since we saw you last. We’ve missed you, boy.”

“Thanks,” returned Bill. “I’m glad to be home again.”

“Which home?” asked his father with an amused smile. “When in New Canaan you seem to spend most of your time across the way here.”

“And why not?” protested Mr. Dixon. “Dorothy and I return the compliment often enough. Since you people moved here two lonely widowers have acquired another child apiece. It’s fine—both Dorothy and I are the happier for it.”

“And that goes two ways,” asserted Bill. “How about it, Dad?”

“Yes, of course,” Mr. Bolton assented heartily. “The intimacy is one I enjoy immensely. But I’m afraid that Bill has begun the habit of leading Dorothy into all kinds of dangerous adventures. This diamond smuggling business, for instance.”

Mr. Dixon chuckled. “If you ask me, I don’t think Dorothy needs any leading.”

“Well, I should say not!” exclaimed his daughter. “If it weren’t for Bill, I’d never be able to get out of half the messes we drift into together!”

Mr. Dixon pushed his chair back from the breakfast table. “This meeting of the mutual admiration society is all very nice,” he announced with a twinkle in his eye, “But it is high time the ways and means committee got together on this last Bolton-Dixon hair-raiser. I vote we adjourn to the porch and learn what the subcommittee on the smugglers’ notebook has to report.”

“Second the motion,” chirped Dorothy. “I’m just crazy to hear what you’ve found out, Daddy Bolton. I suppose Bill has been hitting the hay, like me?”

“He put in nearly sixteen hours of uninterrupted slumber,” Mr. Bolton answered as they found chairs for themselves on the shaded porch, where the air was sweet with the scent of honeysuckle.

“Well, I guess it was a dead heat,” she laughed. “I woke up less than an hour ago, myself.”

Mr. Dixon passed his case to Mr. Bolton and when their after-breakfast cigars were well alight, Bill produced the notebook.

“While you’re busy with that stogie, Dad, I’ll start the ball rolling.”

“Humph! That—er—stogie happens to be a fifty-cent Corona!” snorted Mr. Dixon who was touchy about his smokes.

“Means nothing to me,” replied Bill blandly. “Don’t use ’em myself and—”

“Say, will you please pipe down on cigars—” broke in Dorothy, “and get to the notebook?”

“Oh, what a pun—” groaned Bill, “you certainly—”

“Be still!” ordered his father. “She’s right. Let’s get down to business. Now, here’s the book,” he went on, opening the little volume. “I dried it in our oven and although the writing is blurred, it is still quite legible. As you see, only a few pages have been used, and they show a simple set of flag signals. The red flag means: ‘Meet Steamship.’ The yellow flag stands for ‘A.M.’; the white, ‘P.M.’ Then there are twenty-four flags to designate the hours and half-hours from one to twelve.”

“Is that all?” asked Dorothy, disappointedly.

“Absolutely. The rest of the pages are blank.”

“I remember hearing the men speak of the bosses’ red flag when I was listening outside the cottage,” she said slowly, “and that meant, of course, that Donovan and Charlie were to meet the steamer.”

“Quite. But until we are able to locate the spot where these signals are displayed we won’t accomplish much.”

Bill nodded. “And now that they know we have discovered their method of smuggling, they’ll probably shift their operations from Fire Island Lightship to some other point along the coast.”

“Very likely,” his father acquiesced. “Although it is my opinion they will discontinue, temporarily, and lay low for a while.”

“Still there must be other shipments in transit right now,” suggested Mr. Dixon. “But I suppose they could manage that by sending radios in code?”

Mr. Bolton carefully knocked the ash from his cigar.

“I think that’s beyond the point,” he argued. “We can only surmise what they may or may not do. The government men will watch the ships and the coast. Both Bill and I talked to Washington over the phone just before we came over here. And the officials there believe that the bearded aviator’s plane is a most important factor in the operations of the smugglers. And the Chief wants Bill to find that plane—”

Dorothy snorted derisively. “Well, he doesn’t want much! That airplane won’t fly over the Beach Club again, after this—”

Mr. Bolton smiled at Dorothy’s vehemence. “But you see, my dear, the Washington gentleman thinks that if Bill is able to follow the mysterious amphibian, it will eventually lead him to the headquarters of the gang.”

Bill burst out laughing. “It’s just like telling me to take a handful of salt—and if I can put it on the birdie’s tail, I will eventually catch the birdie! But it isn’t really the Chief’s order, he knows what we’re up against. It’s that assistant of his who wants to cover himself with glory. I asked him if I hadn’t better disguise my plane like a string of white boxes so they’d take me for a diamond necklace!”

“What’d he say?” giggled Dorothy.

“Oh, he spread on the soft soap until I got even more disgusted and turned him over to Dad!”

Mr. Dixon chuckled. “It’s a pretty large order. I don’t suppose your Secret Service friend gave you any valuable suggestions?”

“He did not,” sneered Bill. “That, as he explained, was entirely up to me!”

For several minutes no one spoke.

“We sure are up against it,” sighed Dorothy at last.

“You mean I am,” was Bill’s reply. “The only thing I can do is to start a series of patrols.”

“We will start a series of patrols,” she corrected. “Two planes will be better than one.”

“Just as you say.” Bill showed no enthusiasm. “My idea of something uninteresting to do is to fly around all day, hunting another plane, that’s probably safely housed in its hangar all the time.”

“Oh, don’t be such a wet blanket! If none of us have brains enough to think of a plan to trap that fellow, there’s no use grouching over it!”

“That’s all very well. But where are we going to patrol? You told me, I think, that those lads planned to take you from the warehouse to their headquarters in Connecticut. This state’s not so big when you compare it with Texas or California—but when it comes to locating a single plane—”

“Listen!” cried Dorothy and ran to the porch steps. “Come here—all of you—quick!”

The deep drone of an airplane increased to a giant roar as a smart two-seater swept down toward the house.

“It’s the Mystery Plane!” she shrieked. “The nerve of him!”

On came the amphibian with throttle wide open, just topping the trees at the edge of the lawn. Then the four on the steps saw the pilot drop something overside and zoom upward missing the roof of the house by inches.

“I should say he has nerve—” Mr. Dixon pointed out on to the lawn. “Run out and get that parcel he dropped on the grass, Bill. This business is getting more interesting by the minute!”

Bill brought the package back to the porch.

“Oh, what do you think it is?” Dorothy grabbed Bill’s arm in her excitement.

“Calm down!” said her father, as Bill held out a small box covered with brown paper and sealed with dabs of red wax. “Handle it carefully—there may be explosive in it.”

“I don’t think so—” said Bill, “those things generally run by clockwork. There’s no tick in this box.”

“Come on—let’s open it,” exclaimed Dorothy impatiently. “I’ll bet it’s nothing dangerous. Couldn’t have been dropped from a plane without going off!”

“Wait one minute,” commanded her father. “We’ll be on the safe side, anyway. Don’t touch the thing till I come back.”

He ran into the house.

“Any address on it?” inquired Dorothy.

“Not the slightest bit of writing. If there is any, it’s underneath this outside wrapping.”

Mr. Dixon came out of the house carrying a pail of water, which he brought down to the lawn, where they were waiting.

“Drop that package into the water,” he ordered Bill. “A good soaking will take the sting out of any explosive.”

Dorothy burst out laughing.

“Maybe—but not in this case, Dad. Look, the thing floats!”

She snatched up the package and ripped off the outside paper, disclosing a white cork box, similar to those used for carrying the contraband.

Bill took a knife from his pocket and opened a blade that proved to be a small screwdriver. He took the box from Dorothy and removed the screws from the lid.

“Gee, do you think they’ve sent us a diamond?” she asked jokingly.

“Not a chance. This is a message of some kind, I’ll bet!”

The box was filled with jeweler’s cotton, from the center of which he drew a revolver cartridge. Around it, fastened by a rubber band, there was a small sheet of note paper. The others gathered close as he smoothed out the paper.

Blocked in capitals with a red crayon was the smugglers’ message.

“LAY OFF! THIS MEANS BOTH OF YOU.”

“Aha! And if we don’t lay off, we’ll be plunked with a bullet from a cartridge like this!” Dorothy summed up. “This affair is likely to get exciting before we finish it.”

Mr. Bolton studied the paper then returned it to the box with the cartridge.

“Has it struck you oddly,” he said quietly, “that these people should know that Bill was mixed up in this? That message, of course, is for Dorothy and Bill.”

“Yes, I was thinking of that,” admitted Bill.

“Strange—” cogitated Mr. Dixon. “You two flew from Babylon back here without a stop—and you both went straight to bed. Neither you, nor I, Bolton, have spoken to anyone about their exploits, I’m sure.”

“Somebody must have found out from the servants that our offspring flew back together,” his friend decided. “It could not have happened any other way. Then that fact, added to the glimpse they must have caught of a young man in the Mary Jane with Dorothy, when they rammed the smugglers’ motor sailor off the lightship, gave them a simple line of reasoning. And the joke of the matter is that their warning has done just the reverse from what they figured it would do!”

Mr. Dixon looked puzzled.

“I don’t quite see what you mean?”

“Why, it has given us the only real clue we have to the gang’s whereabouts,” smiled Bolton senior.

“Dad’s one up on me, too,” grinned Bill. “How about you, Dot?”

Miss Dixon stamped her foot. “You’ll dot, and carry one you’ll remember for the rest of your life if you murder my perfectly decent name that way, Bill! You ought to know by now that I won’t stand for it.”

“So sorry, Dorothy!” he apologized with mock politeness. “Will Miss Sherlock Holmes, the famous lady sleuthhound who solved the New Canaan Bank mystery, deign to say whether or not she also spots a clue in the villain’s message?”

“Aren’t you the bunk! Yes, I think I know what Daddy Bolton is talking about.”

“Well, Miss Cleverness, what is it then?”

“Oh, you make me tired! But just to prove that I’m not as dumb as you act, the clue is this—”

“Give me a chance,” begged Mr. Dixon, entering into the spirit of the game. “Your idea, Bolton, is to find out from the servants who they’ve been talking to and trace the smugglers from—”

“Cold as an iceberg,” broke in Mr. Bolton. “I’m sorry to admit it, but you and Bill don’t seem very quick on the uptake this morning. What do I mean, Dorothy?”

Dorothy made a face at Bill.

“We know that these men have headquarters somewhere in this state,” she began airily. “Why? Because Donovan said they must get me over to Connecticut. And later, in the warehouse, he told Peters not to rob me because the boss wanted me delivered just as I was. Daddy Bolton believes that because these men have been spotted so quickly that you are mixed up in it, Bill, their headquarters are much nearer to this house than we figured: that the chances are, it is only a very few miles from here that they’re to be found—or their system of spying on us couldn’t be so perfect!”

“That’s right,” concurred Mr. Bolton. “This smuggler boss or his accomplices over here must live in the neighborhood. Some of his servants know ours—have known them for some time or they would not have been able to ask questions without causing suspicion.”

Mr. Dixon looked suddenly serious. “You can’t mean that our neighbors along this ridge are mixed up in it? The Clarks, old Holloway, the Denbys, Miss Cross—and ten or a dozen others—are all old friends and eminently respectable people! Why, it’s preposterous to think—”

“I’m not trying to pin it on anybody yet,” countered Bill’s father. “But mark my words—when this business is cleared up, you’ll find that some eminently respectable New Canaan household is mixed up in it!”