There came a sudden, inexplicable jar throughout the whole structure of the Sea Ranger. Jack was flung flat on his back. The engines began to roar and race furiously. Every beam and rivet in her frame seemed to vibrate.
"Something terrible has happened," was the thought that flashed through the lad's mind, as he picked himself up.
He rushed out on deck as soon as he could collect his scattered senses. The wind was still screaming angrily, and the riotous sea was leaping all about the Sea Ranger.
But above the turmoil of the storm, Jack caught a startling cry that came through the darkness.
"Help!"
"Tom's voice!" exclaimed the lad.
He stumbled across the heaving deck and rushed up the two steps that led to the bridge where he had left his brother at the wheel. His pulses were throbbing wildly. The next moment, he, too, uttered a cry.
The bridge was vacant! Tom had vanished!
"Help! Help!"
The shout came once more. But it was fainter this time. Jack gazed about him despairingly. Tom was overboard, that much was certain. But how had it happened? How——?