“Keep your head, Tully,” he warned. “The boy’s mad clear through and he’d do just what he said—clean up on both of us. Maybe we’ve got it coming, though. We baited him too much. But we’re going to find that missing radio document.” The same resolution was in Bob’s heart as he stepped down the avenue, but in addition was the grim determination that he would find his uncle. Chapter XXV THE FIRST CLUE ★ The coolness of the fall night helped to clear the mad whirl of Bob’s fatigued mind and he mulled over the things that had happened as he walked down the avenue. For nearly 24 hours the missing paper had been in his possession, which accounted for the attempt to kidnap him. But how had it leaked that the paper had been sent over to the archives division for filing—who had known that he would be alone that night? Bob felt that knowing the answer to this question, he would have something on which to base his further investigation. Then there was the disappearance of his uncle that night. Bob knew that both the radio document and the federal agent were in the hands of ruthless and relentless men. From what his uncle had told him before, the radio secret was worth a huge amount to almost every foreign power and he dared not guess what country might be interested in obtaining its possession through such means as had been employed. Bob’s walk took him to the archives building and he automatically turned in and went up to the office where he worked. The guard on duty on that floor was a familiar one, and Bob spoke to him briefly. “Anything unusual tonight?” he asked. “Not a thing,” was the quick and honest reply. Bob walked down the corridor, unlocked the door of the office, switched on the lights, and stepped inside. The room appeared to be just as he had left it in the afternoon and Bob sat down at his desk. It was quiet here and he would have an opportunity to think out some of his problems. But he found himself too tired even for that. His head was heavy and he drowsed at his desk. Half an hour passed and Bob fell into a sound slumber. For an hour he slept at his desk until the tapping of the guard at the door aroused him. Bob opened the door in response to the summons. “Thought something might have happened to you,” said the guard, half apologetically. “Something did,” smiled Bob. “I went sound asleep. I’d better get out of here and get to bed.” While the guard looked on, Bob turned off the lights, locked the room and started toward the elevator. The guard halted him a few paces down the hall. “Sorry, Mr. Houston, but I’ll have to search you. There’s a new rule that anyone working on this floor out of hours must be searched.” Bob was half inclined to be angry, but he realized the soundness of this rule, especially after what had just taken place. He quietly submitted to a careful search of his clothing by the guard.