A special link that drew the boys still closer together was their common interest in radio. That wonderful new science found no more fervent devotees than they. Almost all their spare moments were spent in increasing their knowledge of its countless marvels, and they had become expert in both receiving and sending. So absorbed did they become that they had gained the name of the “Radio Boys,” and soon it became a matter of course for Castleton folk to refer to them in that way when they were mentioned together. They saw the possibilities of the science, and worked at it not merely as a pastime, but because they had about decided to make it their lifelong profession.

The boys were red-blooded, all-alive young Americans and full of love for adventure. How that zest led them into many perils; how by a curious combination of circumstances they found themselves embarked on the hazardous work of the Secret Service; how their work led them into the Everglades of Florida, where they encountered danger from beasts and reptiles and still more deadly criminals; how often they came within a hair’s breadth of death and yet finally came out triumphant—these things are told in the first volume of this series, entitled: “The Radio Boys in the Secret Service; or Running Down the Counterfeiters.”

Shortly after their return, the bank at Castleton was the victim of a daring holdup. Fifty thousand dollars were stolen and Dick’s father, the cashier, was wounded. It was learned that “Muggs” Murray, the leader of the gang, had been seen in Texas. About the same time the Radio Boys, who were expert aviators, had an invitation to enter the flying service in connection with the Texas Rangers, who were patrolling the troubled Mexican border. The opportunity for more adventure, combined with the chance that they might get on the trail of the robber leader, proved too strong an allurement to be resisted, and they were soon in the thick of the fighting with guerillas along the Rio Grande. How narrowly they escaped death on the land and in the air; their thrilling rescue of prisoners held by the enemy; how Phil himself was taken captive and held for ransom and the part that radio played in his escape; how “Muggs” Murray was tracked and brought to justice can be seen in the second volume of this series, entitled: “The Radio Boys in the Flying Service; or, Held for Ransom by Mexican Bandits.”

They had only been home a few weeks from this last experience when in this singular manner they had been brought in contact with Benton, this other soldier of fortune, who had declared that adventure was the breath of life to him. To all of them had come the impression that this was more than a chance meeting, and that in some way yet to be defined their future was to be bound up with his. It was this feeling that made them await with such intentness the words that he had seemed on the point of speaking.

For a full minute Benton seemed to be debating with himself. Then caution seemed to gain the upper hand, and he looked at them with a whimsical smile that was half apologetic.

“I guess the thing will keep,” he remarked, “and anyway I’m too groggy just now to tell you clearly just what I have in my mind. But I sure do want to see more of you fellows, if you’ll let me.”

“Sure thing,” replied Phil heartily, and the others echoed him. “Just now I think the best thing you can do is to get to town, have a doctor look you over and then settle down for a good night’s rest. Then tomorrow perhaps we can get together again. That is, if your business doesn’t make it necessary to get away from Castleton in a hurry.”

“Not at all,” answered Benton, as he got a little unsteadily to his feet. “In fact, I think Castleton will be the end of my present trip, though I didn’t think so when I started out this morning.”

The remark was rather cryptic, but the boys forbore any further questioning and busied themselves with harnessing up the horse, which seemed by this time to be in a thoroughly subdued frame of mind.

There was not room for all in the buggy and it was arranged that Phil should drive with Benton to the town, while Dick and Tom should follow on foot.