[Ill.u.s.tration]

"Well, I give it up!" declared Doris, after she had stared at it intently for several more silent moments. "It's the strangest puzzle I ever saw. But, do you know, Sally, I'd like to take it home and study it out at my leisure. I always was crazy about puzzles, and I'd just enjoy working over this, even if I never made anything out of it. Do you think it would do any harm to remove it from here?"

"I don't suppose it would," Sally replied, "but somehow I don't like to change anything here or take anything away even for a little while. But you can study it out all you wish, though, for I made a copy of it a good while ago, so's I could study it myself. Here it is." And Sally pulled from her pocket a duplicate of the strange design, made in her own handwriting.

At this point, Genevieve suddenly became restless and, clinging to Sally's skirts, demanded to "go and play in the boat."

"She doesn't like to stay in here very long," explained Sally.

"Well, I don't wonder!" declared Doris. "It's dark and dreary and weird.

It makes me feel kind of curious and creepy myself. But, oh! it's a glorious secret, Sally,--the strangest and most wonderful I ever heard of. Why, it's a regular _adventure_ to have found such a thing as this.

But let's go out and sit in the boat and let Genevieve paddle. Then we can talk it all over and puzzle this out."

Sally returned the tin box and its contents to the hiding-place under the mattress. Then she blew out the candle, remarking as she did so that she'd brought a lot of candles and matches and always kept them there.

In the pall of darkness that fell on them, she groped for the entrance, pushed it open and they all scrambled out into the daylight. After that she padlocked the opening and buried the key in the sand nearby and announced herself ready to return to the boat.

During the remainder of that sunny morning they sat together in the stern of the boat, golden head and auburn one bent in consultation over the strange combination of letters and figures, while Genevieve, barefooted, paddled in silent ecstasy in the shallow water rippling over the bar.

"Sally," exclaimed Doris, at length, suddenly straightening and looking her companion in the eyes, "I believe you have some idea about all this that you haven't told me yet! Several remarks you've dropped make me think so. Now, honestly, haven't you? What _do_ you believe is the secret of this cave and this queer jumble of letters and things, anyway?"

Sally, thus faced, could no longer deny the truth. "Yes," she acknowledged, "there _is_ something I've thought of, and the more I think of it, the surer I am. And something that's happened since I knew you, has made me even surer yet." She paused, and Doris, wild with impatience, demanded, "Well?"

"_It's pirates!_" announced Sally, slowly and distinctly.

"_What?_" cried Doris, jumping to her feet. "Impossible! There's no such thing, nowadays."

"I didn't say 'nowadays,'" remarked Sally, calmly. "I think it _was_ pirates, then, if that suits you better."

Doris sank down in her seat again in amazed silence. "A pirate cave!"

she breathed at last. "I do believe you're right, Sally. What else _could_ it be? But where's the treasure, then? Pirates always had some around, didn't they? And that cave would be the best kind of a place to keep it."

"That's what this tells," answered Sally, pointing to the sc.r.a.p of paper. "I believe it's buried somewhere, and this is the secret plan that tells where it is. If we could only puzzle it out, we'd find the treasure."

A great light suddenly dawned on Doris. "_Now_ I know," she cried, "why you were so crazy over 'Treasure Island.' It was all about pirates, and there was a secret map in it. You thought it might help you to puzzle out this. Wasn't that it?"

"Yes," said Sally, "that was it, of course. I was wondering if you'd guess it. I've got the book under the bow seat of the boat now. Let's compare the things." She lifted the seat, found the book, which fell open of its own accord, Doris noticed, at the well-known chart of that well-loved book. They laid their own riddle beside it.

"But this is entirely different," declared Doris. "That one of 'Treasure Island' is a map or chart, with the hills and trees and everything written plainly on it. This is nothing but a jumble of letters and figures in little squares, and doesn't make the slightest sense, no matter how you turn or twist it."

"I don't care," insisted Sally. "I suppose all secret charts aren't alike. I believe if we only knew how to work this one, it would certainly direct us straight to the place where that treasure is buried."

So positive was she, that Doris could not help but be impressed. "But pirates lived a long time ago," she objected, "and I don't believe there were ever any pirates around this place, anyway. I thought they were mostly down around Cuba and the southern parts of this country."

"Don't you believe it!" cried Sally. "I've heard lots of the old fishermen about here tell how there used to be pirates right along this coast, and how they used to come in these little rivers once in a while and bury their stuff and then go out for more. Why there was one famous one they call 'Captain Kidd,' and they say he buried things all about here, but mostly on the ocean beach. My father says there used to be an old man (he's dead now) right in our village, and he was just sure he could find some buried treasure, and he was always digging around on the beach and in the woods near the ocean. Folks thought he was just kind of crazy. But once he really did find something, way down deep, that looked like it might have been the bones of a skeleton, and a few queer coins and things all mixed up with them. And then every one went wild and began digging for dear life, too, for a while, but they never found anything more, so gradually they left off and forgot it."

Doris was visibly stirred by this curious story. After all, why should it not be so? Why, perhaps could not _they_ be on the right track of the buried treasure of pirate legend? The more she thought it over, the more possible it became. And the fascination of such a possibility held her spellbound.

"Yes," she agreed, "I do believe you're right, Sally. And now that I look it over, these letters and numbers might easily be the key to it all, if we can only work it out. Oh, I never heard of anything so wonderful happening to two girls like ourselves before! Thank you, a million times, Sally, for sharing this perfectly marvelous secret with me."

"I do believe I'm enjoying it a great deal better myself, now that I've told you," answered Sally. "I didn't think it could be so before I did.

And if we ever discover what it all means--"

"Why, precious!" interrupted Doris, turning to Genevieve, who all unnoticed had come to lean disconsolately against the side of the boat, her thumb tucked pathetically in her mouth, her eyes half tearful.

"What's the matter?"

"I'm hung'y and s'eepy!" moaned Genevieve. With a guilty start, Doris gazed at her wrist watch. It was nearly one o'clock.

"Merciful goodness! Mother will be frantic!" she exclaimed. "It's lunch-time now, and we're way up here. And just see the way I look!" She was indeed a scratched, grimy and tattered object. "Whatever will I tell her?" They scrambled to their oars and were out in the river before Sally answered this question.

"Can't you tell her you were exploring up on Slipper Point?"

"Yes," agreed Doris. "That is the real truth. And she never minds if I get mussed and dirty, as long as I've enjoyed myself in some way that's all right. But I hope I haven't worried her by being so late."

They rowed on in mad, breathless haste, pa.s.sed the wagon-bridge, and came at last in sight of the hotel. But as they beached the boat, and Doris scrambled out, she said in parting:

"I've been thinking, all the way down, about that secret map, or whatever it is, and I have a new idea about it. I'll tell you tomorrow morning. This afternoon I've promised to go for a drive with Mother."

CHAPTER VI

WORKING AT THE RIDDLE

But Doris did not have an opportunity to communicate her idea on the following morning, nor for several days after that. A violent three or four days' northeaster had set in, and for forty-eight hours after their expedition to Slipper Point, the river was swept by terrific gales and downpouring sheets of rain. Doris called up Sally by telephone from the hotel, on the second day, for she knew that Sally would very likely be at the Landing, where there was a telephone connection.

"Can't you get well wrapped up and come up here to see me a while?" she begged. "I'd go to you, but Mother won't let me stir out in this awful downpour."

"I could, I s'pose, but, honestly, I'd rather not," replied Sally, doubtfully. "I don't much like to come up to the hotel. I guess you know why." Doris did know.

"But you can come up to my room, and we'll be alone there," she suggested. "I've so much I want to talk to you about. I've thought of something else,--a dandy scheme." The plan sorely tempted Sally, but a new thought caused her to refuse once more.

"I'd have to bring Genevieve," she reminded Doris, "and she mightn't behave, and--well, I really guess I'd better not."

"Perhaps tomorrow will be nice again," ended Doris, hopefully, as she hung up the receiver.

But the morrow was not at all "nice." On the contrary, it was, if anything, worse than ever. After the morning mail had come, however, Doris excitedly called up Sally again.

"You simply must come up here, if it's only for a few minutes!" she told her. "I've something awfully important that I just must talk to you about and show you." The "show you" was what convinced Sally.

"All right," she replied. "I'll come up for half an hour. I'll leave Genevieve with Mother. But I can't stay any longer."

She came, not very long after, and Doris rushed to meet her from the back porch, for she had walked up the road. Removing her dripping umbrella and mackintosh, Doris led her up to her room, whispering excitedly:

"I don't know what you'll think of what I've done, Sally, but one thing I'm certain of. It can't do any harm and it may do some good."

"What in the world is it?" questioned Sally, wonderingly.