do," he said to his two friends as they
reached the deck. "I'd like to hide in the closet in the cabin and watch
that fellow. I bet he'd do something that would help us break his
mysterious silence."

"You could steal down into that little alcove near the entrance of the
cabin and watch him there through the crack in the door," Bud suggested.

"That's second best choice," said Hal, "I think I'll make use of
it at once."

Accordingly he descended the companionway with the greatest caution and
succeeded in ensconcing himself in the position suggested by Bud. He had
not been there long when he was amply rewarded for his diligence.

He could hear the prisoner moving about in the cabin and a peep through
the long narrow aperture along the hinge side of the door acquainted him
with the object of the Canadian boy's interest. The latter, apparently,
had just seated himself at the table, and with phones to his ears, was in
the act of tuning the instrument.

Presently he appeared to be satisfied with this preliminary and put his
hand on the sending key. The fellow seemed to be perfectly at home with
the outfit. Now the key was tapping and the spark was leaping across the
gap. The secret watcher leaned forward eagerly to catch every sound. Yes,
it came in genuine enough dots and dashes, and he read them with ever
increasing astonishment.

First the operator repeated a Canadian call several times. Then,
apparently, the call was acknowledged, and he sent the following message:

"I am prisoner on yacht, Catwhisker, in hands of the fellows I tried to
hold back, with radio, as they were leaving Oswego, N.Y. They are
determined to solve mystery of your doings. Don't bother about me, but
tell pa to clean out his place as soon as possible and then let his
prisoner go. They have government officer with them on his trail and will
soon find his hiding place and raid it."

"My goodness!" Hal breathed excitedly. "Now I'm getting at the bottom
of this affair. That boy is the anonymous amateur who pretended to
have a radio wager with Hal's cousin and tried to make us think his
SOS was a joke."

CHAPTER XXIX

The End of the "Mystery"

Hal almost held his breath in his eagerness to maintain perfect silence
in order that he might "listen-in" to this radio transmission until the
sender had telegraphed all that he had in mind to send.

"My, if I only had an extension receiver," he thought. "How I would like
to hear what the fe