A warning “sst” over the ’phone checked her before she pronounced the name and starting guiltily she turned to look over her shoulder, feeling relieved to see the two men still chatting at the table, apparently paying no attention to her. “I understand,” she answered quickly. “What is it?” “You know that book I told you I was going to buy?” “Yes, yes!” “It’s not there.” “What’s that? The book is gone!” “The book is there all right, but it’s not the book I want.” “Are you sure,” she questioned, “that you looked at the right book?” “I looked at the one you told me to.” “Are you certain—the fifth book on the second shelf.” Illustration: Had he been standing there listening? How much had he heard? She heard a movement behind her and turning quickly saw Frederic Hoff standing behind her, his hat and stick in hand. Panic-stricken, she hung up the receiver abruptly. Had he been standing there listening? How much had he heard? He would know, of course, what “the fifth book on the second shelf” signified. Had her carelessness betrayed to him the fact that he and his uncle were being closely watched? Anxiously she studied his face for some intimation of his thoughts. He was standing there smiling at her, and to her agitated brain it seemed that in his smile there was something sardonic, defying, challenging. “I cannot tell you, Miss Strong, how much I have enjoyed your hospitality. You made the time so interesting that I had no idea it was so late. You will excuse me if I tear myself away at once. I have some important business that demands my immediate attention.” “I hope you’ll come again,” she managed to stammer, “and you, too, Mr. Kramer.” White-faced and terrified she escorted them out, leaving the telephone bell jangling angrily. As the door closed behind them, she sank weak and faint into a chair, not daring yet to go again to the ’phone until she was sure they were out of hearing. What was the “immediate business” that was calling them away so suddenly? She was more than afraid that her incautious use of the phrase “the fifth book on the second shelf” had betrayed her. What else could it mean? Why else would they have departed so abruptly? Mustering up her strength and courage she went once more to the ’phone. “Hello, hello, is that you, Miss Strong? Some one cut us off,” Carter’s voice was impatiently saying. “Hello, Mr. Carter,” she called, “this is Jane Strong speaking. Where can I see you at once? It’s most important.” “I’ll be sitting on a bench along the Drive two blocks north of your house inside of ten minutes.” “I’ll meet you there,” she answered quickly, with a feeling of relief. The situation was becoming far too complicated, she felt, for her to handle alone. Carter would know what to do. If Hoff and Kramer had learned from her about the trailing of old Hoff, the sooner it was reported to more experienced operatives than she was the better.