"Point straight to the north," repeated Clay. "I wonder what that means."
"I'd like to know what any of it means," Alex asserted. "It looks to me like some one was butting in."
"Well," Case remarked, "we have started out on every trip with a mystery to unravel, and here we go again, loaded up with another."
"You bet we have!" laughed Alex. "We harvested gold on the Amazon, caught murderers on the Columbia, found a secret treasure in the Grand Canyon, and chased pirates on the Mississippi, but this is the only real Captain Kidd mystery we have struck yet."
"What shall we do with it?" asked Clay, rattling the paper.
"Throw it in the river and be on our way," proposed Case.
"Suppose," Alex grinned, "there should be a barrel of money in that safe they've made a drawing of. If there is, we want to get it."
"I think we'd better be going on, just the same," Case said. "I'm for dumping this map thing into the river and forgetting all about it."
"Aw," Alex cut in, "that would be throwing away all the fun. I want to go to this 'North,' wherever it is. There may be something funny doing there."
Captain Joe, who had been sitting at the prow, watching the boys with an intelligent interest, now passed back to the cabin, leaped upon the low roof, and bounded to the after deck. The boys heard him growling threateningly for a moment, and then he came back.
Teddy, the cub, arose from the place where he had been lying, sniffed at the gunwale of the boat for an instant, and walked into the cabin.
"What's the matter with our menagerie to-night," demanded Alex. "There seems to be something in the air."
"What do you see, Captain Joe?" asked Clay. "If it's a man, and he's got a letter, you go get it. Some other fellow may be wanting us to go South, or East, or West."
As Clay ceased speaking, the splash of a paddle came faintly from the darkness to the West.
"Here comes R. F. D. postman number two," shouted Alex.
As the boys listened, the splashings of the paddle came louder for a moment, then ceased entirely.
"Hello, the boat!" Alex cried. "Have you got a letter for us?"
No answer came back. There was now a break in the clouds, and the moon shone sharply down upon the swirling river, but only for an instant.