!" 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
mass below her. Toward this mass 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 hoarse 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.

"Did--did you find it?" qu