Next day I started out in search of a copy of _Royal Love Letters_. Of course I failed to get one: it had been out of print for years, as it had been published privately and comparatively few copies had been printed. However, I sent wires to some twenty provincial dealers in second-hand books, and at noon next day had a reply from a dealer in Birmingham, offering me a copy for four and sixpence. I wired the money, and next morning received the shabby little volume. Little did I realise what a dividend my investment of four shillings and sixpence was going to pay me! On reading the book through, I found it was merely a monograph on the published love letters of various royal personages. It was as dull as the proverbial ditch-water, and I was not surprised at the difficulty both Heinrich and myself had experienced in securing copies: the wonder was that any had escaped the fire or the waste-paper basket. But the very fact made Heinrich's interest in the book the more suspicious. It conveyed nothing to me, it is true, about Gotha raids on London, but did it convey anything to Heinrich, or was it the means of conveying anything from him to someone else? I called up Madame Gabrielle on the 'phone, and after she had arrived and examined the volume, we went out to lunch at the Ritz. Across the table I told her of the curious advertisement in the _Petit Parisien_, whereupon she exclaimed: "Why, Kristensten reads that paper regularly. I often see him with it. He goes down practically every column of it with his big reading-glass!" "That settles two points, anyhow," I said. "The first is that he uses that paper for receiving, and perhaps for sending messages. The second is that he knows the spy-cipher used in drawing up the advertisement. I am beginning to feel that this out-of-print and forgotten book will, if we watch carefully, supply us with a very interesting line to follow." And, ringing up Hecq, I told him about the latest development. He was keenly alive to the possibilities of the new situation. CHAPTER TWELVE. THE SECRET OF THE RIBBON. Our new discovery seemed to me so remarkable that I lost no time in impressing upon Madame Gabrielle the imperative necessity of the closest possible scrutiny of Blind Heinrich's actions. I was more than anxious that we should not lose sight of him for an instant, and that I should be kept fully informed of his every action. For by this time I was firmly convinced that, through some medium which we had yet to discover, he was in some way keeping up communication with the more active agents of the enemy. And if we could but discover the channel through which the stream of communications flowed, it would not be long, I felt sure, before we had the key to the mystery in our hands.