Chapter XIII. Koku Saves the Light

"Don't do that!" cried Mr. Whitford.

"What?" asked Tom, in some surprise.

"Don't destroy that letter. It may give us a clew. Let me have it. I'll put a man at work on that end of this game."

"Bless my checkerboard!" cried Mr. Damon. "This game has so many ends that you don't know where to begin to play it."

The government man smoothed out the crumpled piece of paper, and looked at it carefully, and also gazed at the envelope.

"It's pretty hard to identify plain print, done with a lead pencil," he murmured. "And this didn't came through the mail."

"I wonder how it got here?" mused Ned. "Maybe some of the crowd that was here when we started off dropped it for the smugglers. Maybe the smugglers were in that crowd!"

"Let's take a look outside," suggested Mr. Whitford. "We may be able to pick up a clew there."

Although our friends were tired and sleepy, and hungry as well, they forgot all this in the desire to learn more about the mysterious warning that had come to them during the night. They all went outside, and Ned pointed to where he had picked up the envelope.

"Look all around, and see if you can find anything more," directed the custom agent.

"Footprints won't count," said Tom. "There was a regular circus crowd out here yesterday."

"I'm not looking for footprints," replied Mr. Whitford, "I have an idea--"

"Here's something!" interrupted Mr. Damon. "It looks like a lead weight for a deep-sea fishing line. Bless my reel. No one could do fishing here."

"Let me see that!" exclaimed Mr. Whitford eagerly. Then, as he looked at it, he uttered a cry of delight. "I thought so," he said. "Look at this bit of cord tied to the weight."

"What does that signify?" asked Tom.

"And see this little hole in the envelope, or, rather a place that was a hole, but it's torn away now."

"I'm not much the wiser," confessed Ned, with a puzzled look.

"Why, it's as plain as print," declared the government agent. "This warning letter was dropped from an airship, Tom."

"From an airship?"

"Yes. They sailed right over this place, and let the letter fall, with this lead weight attached, to bring it to earth just where they wanted it to fall."

"Bless my postage stamp!" cried Mr. Damon. "I never heard of such a thing."

"I see it now!" exclaimed Tom. "While we were off over the river, watching for the smugglers, they were turning a trick here, and giving us a warning into the bargain. We should have stayed around here. I wonder if it was Andy's