“It’s a funny thing,” he said at last.  “You know I never heard of your shop until a week ago to-day, and now it seems like the most important place on earth.  It was only last Tuesday that we had supper together, and since then I’ve had my scalp laid open twice, had a desperado lie in wait for me in my own bedroom, spent two night vigils on Gissing Street, and endangered the biggest advertising account our agency handles.  I don’t wonder you call the place haunted!”

“I suppose it would all make good advertising copy?” said Roger peevishly.

“Well, I don’t know” said Aubrey.  “It’s a bit too rough, I’m afraid.  How do you dope it out?”

“I don’t know what to think.  Weintraub has run that drug store for twenty years or more.  Years ago, before I ever got into the book business, I used to know his shop.  He was always rather interested in books, especially scientific books, and we got quite friendly when I opened up on Gissing Street.  I never fell for his face very hard, but he always seemed quiet and well-disposed.  It sounds to me like some kind of trade in illicit drugs, or German incendiary bombs.  You know what a lot of fires there were during the war—­those big grain elevators in Brooklyn, and so on.”

“I thought at first it was a kidnapping stunt,” said Aubrey.  “I thought you had got Miss Chapman planted in your shop so that these other guys could smuggle her away.”

“You seem to have done me the honour of thinking me a very complete rascal,” said Roger.

Aubrey’s lips trembled with irritable retort, but he checked himself heroically.

“What was your particular interest in the Cromwell book?” he asked after a pause.

“Oh, I read somewhere—­two or three years ago—­that it was one of Woodrow Wilson’s favourite books.  That interested me, and I looked it up.”

“By the way,” cried Aubrey excitedly, “I forgot to show you those numbers that were written in the cover.”  He pulled out his memorandum book, and showed the transcript he had made.

“Well, one of these is perfectly understandable,” said Roger.  “Here, where it says 329 ff. cf.  W. W. That simply means ’pages 329 and following, compare Woodrow Wilson.’  I remember jotting that down not long ago, because that passage in the book reminded me of some of Wilson’s ideas.  I generally note down in the back of a book the numbers of any pages that interest me specially.  These other page numbers convey nothing unless I had the book before me.”

“The first bunch of numbers was in your handwriting, then; but underneath were these others, in Weintraub’s—­or at any rate in his ink.  When I saw that he was jotting down what I took to be code stuff in the backs of your books I naturally assumed you and he were working together——­”

“And you found the cover in his drug store?”

“Yes.”

Roger scowled.  “I don’t make it out,” he said.  “Well, there’s nothing we can do till we get there.  Do you want to look at the paper?  There’s the text of Wilson’s speech to Congress this morning.”