Polly, sitting in the stern seat, reached for their own lantern and smothered its rays. "We won't show a gleam, either," she muttered.

"Why! who could it possibly be?" cried Wyn. "Do you think somebody may be following us?"

"I don't know," returned Polly, grimly. "But I thought I heard something back there at our house. We were talking loud. If those silver images were worth all Dr. Shelton says they were, there are more than us girls who would like to find them."

"My goodness me! I didn't think of _that_," observed Wyn Mallory, with a little shiver. "Do you suppose we really are being followed?"

CHAPTER XXV

THE STRANGE BATEAU

Polly laughed a little. Yet she spoke seriously.

"You needn't be so worried, Wyn. I know most of the men who do business on the lake. Some of them are mighty fine fellows, and others are just the opposite; but I'm not afraid of the worst of them."

"If they followed us, and we _did_ find the sunken motor boat, couldn't they grapple for the box of silver images, and steal them?"

demanded Wyn.

"Not easily. You see, they don't know where the box was stowed. Father told n.o.body but me. The _Bright Eyes_ was a good-sized boat, and they'd have some trouble getting up the box without raising the boat herself."

"I suppose that's so," admitted Wyn, less anxiously, as the _Coquette_ carried them swiftly toward Gannet Island. "But these men you speak of might interfere with us."

"Yes. That's so. But they'd get as good as they sent, I reckon," said Polly, who didn't seem to have a bit of fear.

Wyn was no coward; she had shown that the time she and Bessie Lavine were spilled out of their canoes in the middle of the lake. But she had not lived, like Polly, in the woods with few but rough people for a.s.sociates.

Soon they pa.s.sed Green Knoll Camp, lying peacefully in the light of the moon that was just then rising above the Forge. Its rays silvered all the knoll and made the camp a charming spot.

"I hope none of them will wake up and find me gone," remarked Wyn, chuckling.

Polly gave the tiller and sheet to her friend and stood up to get a better view of the lake astern of them. At first she saw nothing but the dim sh.o.r.es and the silvering water. Then, some distance out, Polly caught sight of a ghostly sail drifting across the path of moonlight.

"A bateau!" she exclaimed. "And--with the wind the way it is--she must have come right out of our cove, Wynnie."

"Do--do you really think anybody was listening to us when we were talking there on the landing, Polly?" Wyn asked. "And are they aboard _that_ bateau?"

"I don't know. But I know I heard something then."

"But that boat isn't following us."

"It may be. We can't tell. They can watch us just as easily as we can watch them."

But when the _Coquette_ got around to the side of Gannet Island where the boys' camp was established, the shadow of the high, wooded ridge was thrown out so far across the lake that the swimming raft and its neighborhood were in darkness.

The catboat, with her sail dropped and her nose just touching the edge of the float, was quite hidden by this shadow of the island, which was all the darker in contrast with the brilliant moonlight lying on the water farther out.

"I'll carry the kedge to the float," whispered Polly, "and then we'll pay out the line till the _Coquette_ floats about over the spot where you think the thing you hit lies."

"Let's get my canoe out of the way, too," urged Wyn. "Oh! I hope the boys will not wake up."

"What's that light up there?" exclaimed Polly, suddenly.

"That's the spark of their campfire. It's in the rocks, so no harm can come from it; they don't trouble to cover it when they go to bed."

"Now, Wyn--push the boat off."

They worked the catboat from the float for several yards. "Wait,"

whispered Wyn. "Let's try here."

"Are you going to dive?"

"Yes. It will make some splash; but I don't believe I can reach the bottom of the lake otherwise, it is so deep here."

"Careful!" cautioned Polly. "You may hurt yourself on whatever is down there."

"I'll look out," returned Wyn, again filling her ears with cotton. She slipped off the skirt of her bathing suit, too, so as to have more freedom. Then she poised herself for a moment on the decked-over part of the sailboat--a slim, lithe figure in the semi-darkness--and gradually bent over with her arms outstretched to part the water.

As she dived forward she thought she heard a quick exclamation from Polly; but Wyn believed it to be an encouraging cry. At least, she gave it no attention as she clove the water and went down, down, down into the depths of the lake.

She opened her eyes, but, of course, saw nothing but a great, shadowy ma.s.s below her. Toward this ma.s.s she swam eagerly; the lake seemed much deeper than it had by daylight.

Struggling against the uplift of the water, she beat her way down into the depths for more than a minute. That was a goodly length of time for the first submersion. And she did not reach the bottom, nor find any object like the thing she had struck against some hours before.

It was necessary for her to rise. As she turned over, a luminous spot appeared over her head, and toward this spot she sprang. With aching chest she reached the surface, and sprang breast high out of the water--some yards from the catboat. There was a strong current here.

"Polly!" she gasped.

"Sh!" hissed her comrade's voice, in warning.

Surprised, Wyn obeyed the warning. Causing scarcely a ripple in the water, she paddled to the boat. There she clung to the rail and listened. She could not see Polly.

"Dunno where they went to in that cat, Eb," growled a hoa.r.s.e voice out of the darkness.

Wyn darted a glance over her shoulder. There, looming gray and ghostly, was the tall sail they had seen once before. The strange, square-nosed bateau was drifting by, but at some distance. Evidently the catboat was well hidden in the shadow of the island.

Suddenly Polly reached over the edge of the boat and seized Wyn's shoulders. "Don't try to climb in," she whispered. "They'll see or hear the splash."

"All right," breathed back the captain of the Go-Aheads.

"It's Eb Lornigan and some of his friends. Eb is a disgrace to the lake.

He's been in jail more than once," whispered Polly.

But Wyn's shoulders began to feel cold. The night air, after all, was not really warm. "I'm going down again," she whispered.