She had been waiting what seemed an eternity before Van Cleft’s house, when a big machine drew up alongside.  Warren greeted her with a smiling invitation to leave Shirley guessing.  Her willingness to go, she felt, would disarm his suspicions.  The little dinner in the apartment with Shine, Warren and three girls had been in good taste enough:  pretending, however, to be overcome with weariness she persuaded them to let her cuddle up on the couch, where she feigned sleep.  Warren had tossed an overcoat over her and left the apartment with the others, promising to return in a few minutes.  He had said to Shine, “She’ll be quiet until we return—­it may be a good alibi to have her here.”  Then he had disappeared, wearing only a soft hat, with no other overcoat.  Listening at the closed hall door, she heard him direct the elevator man, “Second off, Joe.”  The door was locked from the outside.  The servant’s entrance was locked, all the bedrooms locked, every one with a Yale lock above the ordinary keyhole.  The Chinese cook had been sent out sometime before to buy groceries and wine for the later party.

“But where did you find the note-book?  It may send him to the electric chair.”  Monty Shirley was lighting one of the cigarettes handed him by his host.  He sniffed at it and crushed out the embers at the end.  “This cigarette would have sent me to dreamland for a day at least—­Warren understands as much chemistry as I do.”

“At first I studied the books in the library out of curiosity and then noticed that three books were shoved in, out of alignment with the others on the shelf.  With a manservant in the house, instead of a woman, of course things needed dusting.  But where these three books were it had been rubbed off!  I took out the books, reached behind and found the little leather volume.  It was simple.  I went to his typewriter when I saw that the pages were all typed, and took out some note-paper, from the bronze rack.”

“And then, Miss Sleuth?”

“Don’t laugh at me.  I had heard of the legal phrase ’corroborative evidence,’ so knowing that it would be necessary to connect that typewriter with the book, I rattled off a few lines on the machine.  Here it is:  it will show the individuality of the machine to an expert.”

“You wonderful girl!” he murmured simply.  She protested, “Don’t tease me.  I have watched you and am learning some of your simple but complete methods of working.  I understand you better than you think.”

“Go on with your story,” and Shirley was uncomfortable, although he knew not why.

“That is the end of my tale of woe.  The kitchen being open, I took advantage of the dumb-waiter, as you already know.  It’s fortunate that waiter is dumb, for it must have many lurid confessions to make.  I never saw such an interminable shaft; it seemed higher than the Eiffel Tower.  See how I blistered my hands on the rope, letting myself down.”