Joe was the first to respond, and the sound became louder. Then Herb and Jimmy followed suit, and it was evident that they served as amplifiers, for with each additional hand the music swelled to greater volume.

The boys looked at each other as if asking whether this was all real or if they had suddenly been transferred to some realm of fancy. They would not have been greatly surprised to wake up suddenly and find that they had been dreaming.

But there was no delusion about it and they listened without saying another word until, in a glorious strain of melody, the selection came to an end. Nor did they break the silence until a band orchestra was announced and crashed into a brilliant overture.

While it was still in full swing, Bob had an inspiration. He took off his headphones and clamped them on to the phonograph that stood on a table near by. Instantly the music became intensified and filled the room. When all their hands were on the wire, it became so loud that they had to close the doors of the phonograph.

"Well," gasped Bob, when the last strain had died away and the demonstration was complete, "that's something new on me."

"Never dreamed of anything like it," said Joe, sinking back in his chair. "Of course we know that the human body has electrical capacity and that operators sometimes have to use metal shields to protect the tube from the influence of the hand. And in our loop aerial at Ocean Point you noticed that the receptivity of the tube was modified when we touched it with our fingers."

"Of course, in theory," observed Bob thoughtfully, "the human body possesses inductance as well as capacity, and so might serve as an antenna. But I never thought of demonstrating it in practice."

"So Bob is an aerial," grinned Herb. "I always knew he was a 'live wire,' but I never figured him out as an antenna."

"And don't forget that if Bob is an aerial we're amplifiers," put in Jimmy.

"There's glory enough for all," laughed Joe. "We'll have to tell Doctor Dale and Frank Brandon about this. We've got so many tips from them that it's about time we made it the other way around."

They were so excited about this new development which they had stumbled upon purely through accident that they sat talking about it for a long time until Bob chanced to look at his watch.

"Just have time for the last selection," he remarked, as he reconnected the aerial. "We'll wind up in the regular way this time. It's an aria from Lucia and I don't want to miss it."

He had some difficulty in making his adjustment, as there was a lot of interference at the moment.

"Raft of amateurs horning in," he muttered. "All of them seem to have chosen just this time to do it. I wonder----"

He stopped as though he had been shot, and listened intently. Then he beckoned to the others to adjust their headphones.

Into the receiver was coming a succession of stuttering sounds that eventually succeeded in framing intelligible words. Ordinarily this might have provoked laughter, but not now. They had heard that voice before.

It was the voice of Dan Ca.s.sey!

CHAPTER IV

A PUZZLING MYSTERY

For the second time that evening the radio boys thought they must be dreaming.

Ca.s.sey! Ca.s.sey the swindler, whom they had compelled to make rest.i.tution to the victim he had wronged. Ca.s.sey the thug, whom they had captured in that wild chase after he had looted the safe and nearly killed the operator in the sending station. Ca.s.sey the convict, who, to their certain knowledge, had been sentenced to a long term in prison.

What was Ca.s.sey doing over the radio? That it was that scoundrel they had no doubt. The stuttering, the tones of the voice, the occasional whistle which he indulged in in order to go on--all these things they recognized perfectly. It was the wildest kind of improbability that he had a double anywhere who could reproduce him so perfectly.

Gone now was any thought of the aria from Lucia. Bob motioned frantically to Jimmy to hand him a pencil and a sheet of paper. Then he jotted down the words, as after great efforts they fell one by one from the stutterer's lips. As Bob did this he bent over the paper in frowning perplexity. The words themselves were intelligible, but they did not seem to make sense, nor was there anywhere a connected sentence.

Finally the stammering voice ceased, and after they had waited several minutes longer to make sure that it would not resume, the boys took off their headphones and gazed at each other in utter bewilderment.

"Well, I'll be blessed!" exclaimed Joe. "That villain Ca.s.sey, of all men on the face of the earth! What do you make of it, Bob?"

"I don't know what to make of it," confessed Bob. "It has simply knocked me endways. I never thought to hear of that rascal again for the rest of my life. Yet here he is, less than a year after he's been sentenced, talking over the radio."

"Perhaps he's received a pardon," hazarded Jimmy.

"Not at all likely," answered Bob. "It isn't as though he were a first offender. He's old in crime. You remember the raking over the judge gave him when he sentenced him. Told him if he had it in his power he'd give him more than he actually did. No, I think we can dismiss that idea."

"Isn't it possible," suggested Herb, "that he's employed as radio operator in the prison? He understands sending and receiving all right."

"That doesn't strike me hard either," Bob objected. "Likely enough the prison is equipped with a wireless set, but it isn't probable that they'd let a prisoner operate it. It would give him too good a chance to get in touch with confederates outside the jail. Then, too, his stuttering would make him a laughing stock.

"The only explanation that I can see," he went on, "is that he's escaped, and he's sending this message on his own hook. Though what the message is about is beyond me."

"Just what did you get down?" asked Jimmy curiously. "I caught a few words, but I don't remember them all."

"It's a regular hodgepodge," replied Bob, spreading out the sheet of paper, while they all crowded around to read.

"Corn--hay--six--paint--water--slow--sick--jelly," read Joe aloud.

"Sounds to me like the ravings of a delirium patient."

"And yet I'm sure that I got all the words down right," said Bob perplexedly. "It must be a code of some kind. We can't understand it, and Ca.s.sey didn't mean that any one should except some one person whose ear was glued to a radiophone. But you can bet that that person understood it all right."

"I wonder if we couldn't make it out," suggested Herb.

"No harm in trying," said Joe, "though compared to this a Chinese puzzle is as simple as A B C. Let's take a hack at it, anyhow. We'll each take a separate sheet of paper and try to get something out of it that makes sense."

For nearly an hour the boys did their best. They put the words in different orders, read them forward and backward. But the ideas conveyed by the separate words were so utterly dissimilar that they could frame nothing that had the slightest glimmering of sense and they were finally compelled to give it up.

"If time were money, we'd spend enough on this stuff to make us bankrupt," Joe remarked, in vast disgust, as he rose to get his cap.

"Dan Ca.s.sey was foxy when he made this up. We'll have to give the rascal credit for that."

"Yes," admitted Herb, "it's the best kind of a code. Any one of those words might mean any one of a hundred thousand things. A man might spend a lifetime on it and be no nearer success at the end than he was when he started. The only way it can be unraveled is by finding the key that tells what the words stand for. And even that may not exist in written form. The fellows may simply have committed them to memory.

"I'll tell you what I'll do!" Bob exclaimed. "I'll get the prison to-morrow on the long distance 'phone and ask them about Ca.s.sey. I'll tell them all about this radio message, and it may be a valuable tip to them. They may be able to locate the station from which the messages come, if there are any more of them. You remember how Mr. Brandon located Ca.s.sey's sending station the first time."

Bob was as good as his word, and got in communication with the prison just before school time. The warden was gruff and inclined to be uncommunicative at first, but his manner changed remarkably after he heard of the radio message and he inquired eagerly for the slightest details.

"Yes, Ca.s.sey has escaped," he told Bob. "He got away about two months ago. He had behaved himself well for the first six months of his imprisonment, and we made him a trusty. In that capacity he had access to various parts of the prison and occasionally to my own quarters, which are in a wing connected with the prison. In some way that hasn't yet been discovered he got possession of clothes to cover his prison uniform and got away one day from the yard in which he was working.

Probably with his help, two others got away at the same time. Their names are Jake Raff and Toppy Gillen, both of them desperate criminals and in for long terms. Likely enough the three of them are operating together somewhere. We made a careful search for them and have sent out descriptions of them to the police of all the important cities in the United States. But this clue of yours is the only one we have, and it may prove a most important one. I'll see that the Federal radio authorities are notified at once. Keep in touch with me and let me know if you come across anything else that seems to point to Ca.s.sey. His escape is a sore point with me, and I'd be glad to have him once more behind the bars. You can be sure he'll never get away again until he's served out the last day of his sentence."

With a warm expression of thanks the warden hung up his telephone receiver, and Bob hurried off to school to tell his comrades of what he had learned.

There was no chance for this, however, before recess, as he had been kept so long at the telephone that he was barely able to reach the school before the bell rang.

When at last he told them of his talk with the warden, they listened with spellbound interest.