“That was an electric gun,” Dave laughed. “We use it while we’re exploring the sea-bottom on foot. If some big fish, like a shark, gets too curious—we touch him and pull the trigger. Believe me, they beat it!
“It’s lucky I had it,” he added. “Otherwise I’m afraid I should have been obliged to kill our prize, and that would have been a great loss. By the way, Johnny, how did that fellow get into the tank?”
“Tumbled in, I suppose. Probably thought he was going down into the hold to prowl around.”
“I wonder why?” said Dave.
But Johnny didn’t see fit to discuss the matter further.
After the others had retired again, Johnny took the stranger’s knife to the light and examined it closely. Never had he seen such perfect workmanship. The blade was of hand-forged steel, with a handle of old ivory. Two foreign words were stamped on the blade. Johnny could not read them, but he knew very well this was no native’s knife.
“A spy, beyond a doubt,” he muttered. “Wonder how many there will be tomorrow night. Dave must let me have a gun!”
Just then the moon came out from behind a cloud, flooding the deck with white light. What a difference that made. All the mystery of the night seemed to fade.
Johnny shrugged his shoulders and continued to pace the deck.