“We’ve got to have more help,” decided the intelligence officer when an hour had slipped away and they had gone through only one bale. He went to a telephone and called the Department of Justice, with the result that within half an hour six other agents were on the job, delving through the growing pile of papers. By noon they had examined every scrap of paper from five bales and their arms and backs were aching sharply. “I’m dizzy,” confessed the intelligence officer when they finally stopped for lunch. Leaving one of the agents to guard the bales in the basement, the others went to a nearby restaurant. Lunch was eaten quickly and with a minimum of talk, for every one of them knew that perhaps a man’s life hinged on the quickness with which they could find the tell-tale envelope. They carried a tray of lunch back to the agent who had been left on guard and plunged once more into the mountainous task which still faced them. The early hours of the afternoon slipped away. Bale after bale of paper was scanned with care and Bob felt his hopes sinking. Another bale was finished and one more pulled down and clipped open. He knelt down again and picked up a handful of waste paper. An envelope drew his attention, but it was for another resident on the floor on which the filing chief lived. Lieutenant Gibbons, whose lanky form was almost doubled in a knot from the hours of bending down and looking at slips of paper, suddenly straightened up with a triumphant cry. “Here’s the letter!” he cried, waving a badly torn envelope. The federal men, dropping the paper they had been sorting, rushed to his side. Bob was the first to see the postmark on the envelope. It was marked from Rubio, Maryland, and was addressed to Arthur Jacobs. The handwriting on the envelope was large and heavy and the pen which had been used was none too good for it had dropped ink in two places on the envelope. Bob felt his heart leap. This was the clue they had sought for so many weary, back-breaking hours in the litter of paper in the basement. “How far is it to Rubio?” Bob asked the intelligence officer. “I’m not sure that I even know what part of Maryland it’s in, but I believe if we go by plane, we should be there in an hour.” “Then we’ll go by plane,” decided Bob. Just how he could obtain a plane was a question he couldn’t have answered at the moment, but he was determined to make the trip with the least possible loss of time for he felt that either in Rubio or near it he would find the solution to the mystery. Chapter XXIX INTO THE AIR ★ Bob and Lieutenant Gibbons left the other federal agents at the apartment building to help the superintendent clean up the litter of paper they had strewn about the basement while they hastened back to the Department of Justice building. Waldo Edgar himself was waiting for their report and he smiled contentedly when he heard it.