"You must find some excuse for me to come up into your apartment and see to it that none of your people are about."
"That will be easy. Mother and Aunt will be out all day, and it is cook's afternoon off. I can easily send the maids out."
"But that's not all. There is the Hoffs' servant to be disposed of."
"I don't see how I can manage that," said Jane. She could think of no possible way of overcoming that difficulty.
"She's an old German woman--Lena Kraus," continued Dean. "I've found out that she always washes on Wednesdays. When she goes up on the roof in the afternoon to get the clothes will be our time. It will be your job to see that she stays there until I am through. It will not take me more than half an hour."
"But what will I do if she starts to come down? How will I stop her?"
"You'll have to use your wits. Keep her talking as long as you can. When she starts down come with her. Press the elevator button four times.
I'll leave the door of the Hoff apartment open and very likely will hear it in time to get away."
"But how'll you get their door open?"
Dean smilingly drew forth a key.
"I borrowed the superintendent's bunch last night, pretending I had lost the key to my locker in the basement. I knew he had a master-key that unlocks all the apartment doors, and there was no trouble in picking it out. I had some wax in my hand and made an impression of it right under his nose."
"How clever," cried Jane, "but suppose the Hoffs do not go off to-morrow. What will we do then?"
"You are taking tea with young Hoff this afternoon, aren't you?"
"Yes," said Jane, "that is, he asked me to. I am to meet him at the Biltmore at five."
"When you're with him propose doing something together to-morrow afternoon. See what he says."
"That's an excellent idea. I'll ask him to go to the matinee with me."
"That will do splendidly. Has he been with that navy officer lately?"
"Not since Sunday, to my knowledge. I wonder if old Mr. Hoff has left any more cipher messages at the bookshop?"
"No," said Dean, "he hasn't. The place has been constantly watched, but he hasn't been near it since that first day."
"I'm afraid," sighed Jane despondently, "I betrayed the fact that we were watching them to the nephew. He overheard me talking to Carter about the 'fifth book,' and of course he knew what it meant. I'm certain the old man is still reporting about our transports. Every day I can hear some one telephoning to him. He waits for the message, and then he goes out."