"I will try to be there," said Lena. "I also have a message for you, but I don't know whether I should say it now or not; those blamed detectives are on to us." There ensued another pause while Bob became more and more excited. What was this plot anyway that turned old and trusted servants against their masters? Was no one to be relied upon? Who could be trusted? "Yes, I will tell Heinrich," said Lena speaking again. "Good-by." She hung up the receiver and Bob continued up the stairs, whistling and trying to act as if he had heard nothing. He met Lena in the hall and she eyed him narrowly. "Hello, Lena," he exclaimed cheerfully. "Fine day, isn't it?" "Yes, Mr. Bob," she said, and passed on toward the back stairs. No sooner was she gone than Bob turned and sped down stairs again to the library. He burst into the room breathlessly, causing his father, who was reading his evening paper to glance up in surprise. "Father," exclaimed Bob in a tense whisper, "Lena's in it too." "What's that?" demanded his father. "Sit down, Bob." Bob grasped a chair and sat down facing his father. "Lena's in it too," he repeated. "In what?" "In the plot with Mr. Wernberg." Mr. Cook laid down his paper. "Tell me what you know," he said soberly. Bob repeated the part of Lena's telephone conversation that he had heard. "You see," he exclaimed, "she spoke about the hospital and that must have meant Mr. Wernberg; then she said the detectives were on to them; finally she said she'd tell Heinrich and also try to be there to-night." "You don't know what she is to tell Heinrich and where she is to be to-night?" "No, sir," said Bob. "That's all I heard." "Well," exclaimed Mr. Cook after a moment's pause. "This is a nice state of affairs." "What are you going to do about it?" asked Bob. "Are you still going to wait until to-morrow before you report Heinie to the police?" Mr. Cook passed his hand across his brow as if to wipe away the doubts that assailed him. "Heinrich and Lena both," he muttered. "What a pity." "I tell you what I'll do," he exclaimed finally. "I'll take Heinrich along with me to-night just as I planned, and I'll tell your mother under no conditions to let Lena go out this evening. In the morning we may know better what to do." "I have a better scheme than that," said Bob eagerly. "Tell me what it is." "Take Heinrich along with you and watch him all the time; that part is all right. But let Lena go out if she wants to." "What's the point of that?" demanded his father. "For all we know Lena may he able to do more harm than Heinrich; certainly she's smarter." "Let her go out," said Bob, "and I'll go with her." "I don't see what you mean." "I'll follow her." "You'd have to be disguised." "I know it; I'll attend to that though." "It might lead you to some very dangerous spot," said Mr. Cook. "I hate to have you do it."