“Then that’s solved, I think,” declared Mr. Henderson. “If you had taken down the phone receiver and had kept your hand upon it you would probably have heard the other speaker’s voice plainly.”

“Gosh, why didn’t we think of that!” interrupted Frank. “And come to think of it, the phone is on the same table with the radio set at Henry’s house.”

“Well, we’ve laid one ghost, we’ll assume,” went on Mr. Henderson, “but that does not solve the mystery of the other speaker nor does it eliminate the possibility that these fellows may be crooks. In our work, you know, we always assume that every suspect is guilty until we prove our theory wrong and so we’ll assume that your mysterious speaker is a crook until we find we’re mistaken. However, before I take any active steps I think it will be a good plan to try another test. Suppose you listen in for a few nights more and, as soon as you hear this fellow, take down your phone receivers and hold the instrument against your body or arm and see if you get the voice of the other chap. Let me know the results and then we can plan our next move.”

“Hurrah! Now we are real radio detectives working for the government!” cried Tom enthusiastically. “Do you really think they’re bootleggers?”

“I make it a point never to form a hard-and-fast opinion,” replied Mr. Henderson with a smile at the boys’ excitement. “However, I should not be in the least surprised if they are, and if so

and we round them up, Uncle Sam will have to thank you boys. Go to it, boys! Perhaps we may have to organize a radio detective corps yet, and I’m not sure that boys may not be able to show us old hands a few tricks at our own game.”

[CHAPTER IV—THE BOYS DRAW A BLANK]

Hardly had the door to Mr. Henderson’s office closed behind them before Frank commenced to dance and caper wildly about.

“Hurrah!” he shouted. “This is great! We’re real detectives and working for Uncle Sam!”

“Yes, but don’t make such a row,” cautioned Tom. “We don’t want every one in the place to know it and they’ll think you’re crazy. Come on, let’s hurry and tell Henry.”