“Here are the fellows that smashed my window!” cried Mr. Larsen, the proprietor of the drygoods store, rushing up to them and shaking his fist in their faces. “Where are the police?” he shouted, looking around him. “I’ll have them arrested for malicious damage.”

And while he faced them, gesticulating wildly, his face purple with anger and excitement, it may be well for the benefit of those who have not read the preceding volumes of this series to tell briefly who the radio boys are and what had been their adventures before the time this story opens.

The acknowledged leader of the boys was Bob Layton, son of a prosperous chemist of Clintonia, in which town Bob had been born and brought up. Mr. Layton was a respected citizen of the town and foremost in its civic activities. Clintonia was a thriving little city of about ten thousand population, situated on the Shagary River, about seventy-five miles from the city of New York.

Bob at the beginning of this story was about sixteen years old, tall and stalwart and a clean-cut specimen of upstanding American youth. He was of rather dark complexion and had a pair of eyes that looked straight at one. Those eyes were usually merry, but could flash with indignation when circumstances required it. He was never on the lookout for trouble, but was always ready to meet it half way, and his courageous character together with his vigorous physique had made him prominent in the sports of the boys of his own age. He was a crack baseball player and one of the chief factors of the high school football eleven. No one in Clintonia was held in better liking.

Bob’s special chum was Joe Atwood, son of the leading physician of the town. Joe was fair in complexion and sturdy in makeup. He and Bob had been for many years almost inseparable companions, Bob usually acting as captain in anything in which they might be engaged, while Joe served as first mate. The latter had a hot temper, and his impulsiveness sometimes got him into trouble and would have involved him in scrapes oftener if it had not been for the cooler head and steadying influence of Bob.

Two other friends of the boys who were almost always in their company were Herb Fennington, whose father kept a large general store in the town, and Jimmy Plummer, son of a respected carpenter and contractor. Herb was of a rather indolent disposition, but was jolly and good-natured and always full of jokes, some of them good, others poor, which he frequently sought to spring on his companions.

Jimmy was a trifle younger than his mates, fat and round and excessively fond of the good things of life. His liking for that special dainty had gained him the nickname of “Doughnuts,” and few of such nicknames were ever more fittingly bestowed.

Apart from the liking that drew them together, the boys had another link in their common interest in radio. From the time that this wonderful new science had begun to spread over the country with such amazing rapidity, they had been among the most ardent “fans.” Everything that they could read or learn on the subject was devoured with avidity, and they were almost constantly at the home of one or the other, listening in on their radio sets and, lately, sending messages, in the latter of which they had now attained an unusual degree of proficiency.

In decided contrast to Bob and his friends was another group of Clintonia youth, between whom and the radio boys there was a pronounced antipathy. The leader of this group was Buck Looker, a big overgrown, hulking boy, dull in his studies and a bully in character. His two special cronies were Carl Lutz, a boy of about his own age, and Terry Mooney, both of them noted for their mean and sneaking dispositions. Buck lorded it over them, and as his father was one of the richest men in the town they cringed before him and were always ready to back him up in any piece of meanness and mischief.

The enthusiasm of Bob and his friends for radio was fostered by the help and advice of the Reverend Doctor Dale, the clergyman in charge of the Old First Church of Clintonia, who, in addition to being an eloquent preacher, was keenly interested in all latter-day developments of science, especially radio. Whenever the boys got into trouble with their sets they knew that all they had to do was to go to the genial doctor and be helped out of their perplexities.