"Then drop your gun!" Bud snapped. Tom, meanwhile, had followed up his first advantage with a stunning blow to the solar plexus. Packy grunted for breath, then came back viciously with several well-aimed punches that staggered Tom. As the young inventor stumbled backward, Packy dived for his gun. Though still groggy, Tom managed to kick the weapon out of reach. Before Packy could straighten up, Tom followed with a sweeping uppercut that caught him squarely on the chin. Packy went down like a felled tree! Tom picked up the gun before his groaning victim could recover. By this time, Bud had pounded his own opponent into submission. Within a few moments, both thugs were lined up against the wall of the cabin. Their wrists were tightly strapped behind them with their own belts. "Oh ... thank goodness!" Sandy gasped. Tom gave the girls a reassuring grin. "Are you two all right?" "I g-guess so." Phyl gave a nervous smile. Now that the tables were turned, it was the thugs' turn to "march." The boys herded them warily back down the hillside toward the road, where Bud had parked his red convertible. Sandy and Phyl followed close behind. [Illustration: _Tom and Bud hurled themselves at the thugs_] Like all cars belonging to the Swifts' key personnel, Bud's was equipped with a two-way shortwave radio. Tom switched it on and radioed Shopton Police Headquarters. Chief Slater promised to send a squad car at once. Minutes later, they heard it approaching. Two husky police officers leaped out as the car braked to a halt, and took charge of the prisoners. Scowling and sullen, they were driven off to jail. "Well," said Bud jokingly, "what about that relaxing hike we were starting?" Phyl sighed. "I'm afraid you two boys just can't get away from _in_ventions and _ad_ventures." Sandy added, "I suggest we go home for a nice safe dinner." Later, at the Swifts' house, Tom received a telephone call from Chief Slater. He reported that the two prisoners were known hoodlums from a nearby city. "They claim they were hired for this job last night by a stranger who spoke with an accent," Slater went on. "According to their story, they never even got a look at his face, and they had no idea he was an enemy agent." "Sounds reasonable," Tom agreed. "It's not likely Mirov's Brungarian henchmen would endanger their whole setup by taking any cheap gunmen into their confidence." Chief Slater also reported that Len Unger was still at large. "But the FBI will probably pick him up soon," he added. "I sure hope so," Tom said. A ten-hour sleep that night proved a fine tonic. Tom awoke the next morning feeling entirely refreshed, and after a hearty breakfast, hurried off to the plant. Here he plunged into work on his quality analyzer sonar. Much of the circuitry was assigned to the electronics department. The finished boards and sub-assemblies were fed back to Tom in his private laboratory. He himself assembled the major units.