“Very possible,” Mr. Evans agreed. “Anyway, a little quick figuring would locate the spot on the sand bar where the men had dropped the cylinder. A Geiger counter could pinpoint it quickly. The diver would recover the cylinder, climb into his rubber boat, and paddle back out—” His words dwindled away to thoughtfulness. “Paddle back out to what?” The man from Drake Ridge voiced the thought that was in all their minds. Eddie wondered if the same answer that immediately occurred to him was shared by the others. Although soon after the article had appeared in the Oceanview newspapers most readers had discarded it as nothing more than an unfounded rumor, Eddie had never quite forgotten it. Nor had the Coast Guard officially withdrawn its belief of what had been sighted by its radar equipment that Saturday night two weeks ago. Now there seemed no argument. It was, in fact, the only logical method by which the isotope and the plans could be smuggled away without detection. “The submarine!” Eddie exclaimed. CHAPTER ELEVEN The parts of the mysterious jigsaw puzzle had begun to fit into a rough pattern, with Eddie and Teena furnishing most of the key pieces. Mr. Evans glanced at his wrist watch. “It’s now a quarter after five,” he said. “The supposed submarine sighting took place on a Saturday night two weeks ago. That same day Eddie and Teena saw the men out over the sand bar. They saw them again last Saturday. Probably another pickup took place that night. It’s logical, therefore, to assume that the third pickup is scheduled for tonight. That doesn’t give us much time to set our trap.” “You’re the boss,” Mr. Taylor said. “You tell us what you want us to do.” “That’s right,” Teena’s father said anxiously. “I can’t overemphasize how important it is that those blueprints don’t get out of this country.” “First I have several urgent phone calls to make,” the FBI man said quickly. “Must get the wheels turning at once.” “There’s a phone in the empty office next door,” Mr. Taylor volunteered. “Help yourself.” While the federal investigator was in the next room telephoning, Mr. Taylor, Mr. Ross, and the man from Drake Ridge talked over what they knew so far. “Apparently what we have to go on,” Eddie’s father said, “are some assorted guesses, none of which may prove to be positive facts.” “Well, guesses will have to do for the moment,” Mr. Ross said. “We have to have a starting point.” “All right,” Mr. Taylor agreed, “here’s what we have. Two men seem responsible for both the stolen isotope and the missing blueprints. Eddie and Teena both saw the tall one called Simms on the college campus about a week ago. He must be familiar with our atomic-research department in order to know of the delivery, and to plan a method for stealing the isotope. In that case, he shouldn’t be difficult to trace.”