this way and, as soon as you hear him, write down what he says. We’ll listen too, whenever we have a chance, and will let you know. Then, if you haven’t picked him up, you can turn the loop until you do. Too bad you haven’t a sending set so you could tell us.”

“But he’ll hear you and quit,” objected Henry, “and how can I hear you if I don’t happen to have the loop pointed your way or am listening to this fellow?”

Frank looked puzzled. “Gee!” he ejaculated, “I hadn’t thought of that.

“Oh, that’s easy,” declared Tom. “You’ll hear us over the other set with the loud-speaker you have. That works with a regular aërial and is

entirely separate from this set. And we’ll arrange a code so he won’t know what we’re talking about. Let’s see, I guess we’d better use the phone and not send dot and dash, we’ll just say ‘we’ve got the message’ and you’ll know what it means.”

“No, that’s no good,” declared Frank. “That’s not a bit mysterious or exciting. We’re radio detectives, you know. We must have something like a password or code or something. Say, let’s begin with ‘loop,’ then Henry’ll know we mean him. We’ll say ‘loop, be ready to receive.’”

“Yes, and have him know something’s wrong when we don’t begin to send anything,” said Tom.

“I have it!” exclaimed Henry, “Say, ‘loop, coming over,’ and then any one’ll think you are telling me you are coming over here. But say, how’ll I get your message if I don’t sit at my set and tune to you?”

“That’s easy,” said Frank. “Just as soon as we get home to Tom’s we’ll begin to send and you listen and tune until you get us good and loud and then mark your knobs so you can set ’em whenever you want to hear us. Then ring us by regular phone and tell us it’s O. K.”

Thus, all being arranged, Tom and Frank went up town and as soon as they reached Tom’s room began to send calls for Henry as they had agreed. Very soon the telephone bell rang and Tom ran to the instrument.

“It’s all right, Frank,” he announced as he returned to the room. “Henry says he got our calls finely and has marked his knobs. He’s going to turn them about and then set them back at the marks and we’re to call him again. Then if he gets us right off he’ll know he won’t miss us next time.”

When, a few minutes later, the phone rang again and Henry told Tom that the message had come in on the adjusted set the boys felt sure that their fellow conspirator would not miss any calls they might send him. So, having nothing else to do, they worked at another step of amplification for their new set, and listened for any signals or messages that might come in from the person whom they were endeavoring to trail by means of radio.

Evidently, however, the mysterious stranger had no business to transact and no message from him was received. When at last they were obliged to

leave for dinner they phoned to Henry who reported that he had been listening all the afternoon, but had heard nothing.

“We’ll get at it again to-night,” said Tom. “Most of the messages we’ve heard come in just when the broadcasting stations are giving their concerts. I’d bet he takes that time so nobody will hear him, or pay attention to him. If they’re all tuned to 360 meters they’d never know he was talking, you see, and if they just chanced to hear him they’d be too busy with the music to bother with him.”

As Tom had suspected, the mysterious messages did come in that night and so interesting and exciting did they prove to the boys’ imaginative and suspicious minds that they were thankful they had foregone the pleasure of hearing the concert on the chance of the supposed smugglers talking.

CHAPTER III—THE RADIO DETECTIVES

The instant the boys recognized the long-awaited signals, Frank called Henry and notified him as agreed and, to their delight and satisfaction, the mysterious stranger continued to talk, evidently paying no heed to the seemingly innocent words of the boys, if indeed he had heard them.

As heretofore, much that was said meant nothing to the boys, but wisely they jotted every thing down nevertheless. However, both Tom and Frank were more puzzled than ever, for now that their minds were concentrated on the messages they suddenly realized that a true conversation, an interchange of messages, was going on, but, for some inexplicable reason, they could hear but one of the speakers. It was like listening to one individual talking to another over an ordinary telephone and the boys could merely guess at the words of the inaudible speaker.

“Yes, it’s all right,” came the words on the easily recognized short waves, “thirty-eight fifty seventy-seven; yes, that’s it. Still there. Gave them the ha, ha! Azalia. Can’t get anything on her. How about Colon? French Islands? Sure, they’re just about crazy. No, no fear of that. Good stuff. No, no rough stuff. Expect her at same place about the tenth. No, don’t hang around. Cleared the third. Fifteen seconds west. I’ll tell him. Good bottom. Good luck! Don’t worry, we’ll see to that. No risk. So long!”

As the conversation ceased Tom jumped up. “Gee!” he exclaimed. “That’s the most we’ve heard yet. I wonder if Henry got it.”

Hurrying to the telephone, he was about to call Henry when the bell tinkled. “Hello!”—came the greeting in Henry’s voice as Tom took down the receiver. “This is Henry. Say, did you get it?”

“You bet we did!” Tom assured him gleefully. “What did you make out? No, guess you’d better not tell over the phone. We’ll be down there right away.”

“He’s east of here,” declared Henry, when Tom and Frank reached his home.

“Golly, he must be in Brooklyn or out on the river!” exclaimed Tom. “What did you make out that he said?”

Henry showed them the message as he had jotted it down and which, with the exception of one or two words, was identical with what they had heard.

“I couldn’t catch some of the words,” explained Henry. “There was a funny sort of noise—like some one talking through a comb with paper on it,—the way we used to do when we were little kids—say, what’s it all about anyway?”

“We don’t know,” replied Frank. “Did you hear any one else talking or anything?”

“And, Henry, were the sounds weak or faint to you?” put in Tom.

“Only that queer sound I told you about. The words were fine and strong here.”

“Then he’s nearer here than he is to us,” announced Tom. “But I would like to know who the other fellow was and what he said and why the dickens we can’t hear him when we hear this chap. Couldn’t you make out any of the words that the fellow said—those that sounded like talking through a comb, I mean?”

“No, they were just a sort of buzzy mumble,” replied Henry.

“Well if he’s east of here it ought to be easy to locate him,” remarked Frank. “Do you know any fellows around here who have sets, Henry?”

“Sure there are lots of ’em,” Henry assured him. “Tom Fleming over at Bellevue has a dandy set and there’s ‘Pink’ Bradley down on 19th St., and Billy Fletcher up on Lexington Ave., and a whole crowd I don’t know.”

“Well, let’s try it out at Fleming’s place next, then,” cried Frank. “Do you s’pose you can see him to-morrow and tell him the scheme? And say, ask him if he’s heard the same talk.”

“I can phone over to him now—I guess he’s home,” said Henry, “but what’s back of all this? You fellows aren’t so keen just because you want to locate this fellow that’s