“You’re on the right track, Bob. Follow it hard and don’t let a single trick get away from you. How are you going to Rubio?” Bob turned to a wall map which showed the entire state of Maryland. As Lieutenant Gibbons had surmised, Rubio was on the east shore, a tiny dot of a town, well isolated from any of the other shore villages. “That’s a desolate stretch,” said the chief. “You may need help in rounding up this gang.” “We’ll try it alone,” said Bob. “If we find them, we can send in a call for assistance. Can you arrange for us to fly there?” The chief of the division of investigation looked at his watch. It was just three o’clock. “A plane will be ready in half an hour at Antacostia,” he said. “Make sure that you are well armed and don’t take unnecessary risks. Understand?” “Yes, sir,” replied Bob. “Then start for Antacostia at once. You’re going, too, lieutenant?” “I wouldn’t miss this,” replied the intelligence officer. “Besides, we have a considerable stake in this game.” “Splendid. But don’t let Bob take any needless risks. I’m counting on his developing into one of my aces one of these days.” Bob’s temperature rose about three degrees and he looked at the federal chief to see if he was joking, but Waldo Edgar was serious. “Looks to me like you’re making headway rapidly,” said Lieutenant Gibbons as they left the Department of Justice building. “You carrying a gun?” he asked. Bob patted his coat pocket. “I’ve got a special .45 with an extra clip of cartridges. That ought to be enough for a trip like this.” “Let’s hope so,” said the intelligence officer. When they reached Antacostia, a cabin plane, a navy ship, was out on the ramp waiting for them. It was an amphibian and while they were paying the driver of their cab, the pilot started the motor with a roar that shook the ground. An officer ran toward them. “Which one of you is Bob Houston?” he asked. Bob stepped forward. “You’re wanted on the phone at once,” he said. “Step on it, Bob. We’re ready to go,” warned Lieutenant Gibbons. Bob ran toward the administration building and a clerk there handed him a telephone. Bob recognized instantly the voice of the chief of the bureau of investigation. Waldo Edgar, usually so calm, was deeply moved. “Bob, get to Rubio with all possible speed. We’ve just had reports that an unknown yet tremendously powerful radio station has just come on the air. The Department of Commerce has had radio direction finders on it for the last ten minutes and they report that the station must be on the east shore of Maryland, probably near Rubio. They’re throwing on extra power on their experimental station here to gum up the sending from this unknown outfit. I’m afraid they’re trying to get the secret of the radio-controlled plane out of the country in this way.” “We’re all ready to go. The plane’s on the ramp now with the motor on.”