By this time Aubert had arrived from Paris, and had taken an obscure lodging in Chessington Street, a dingy thoroughfare off the Euston Road. By appointment I met him late one night at the corner of Grey's Inn Road and Holborn, and, having explained to him briefly what had occurred, told him to hold himself in readiness for instant action. The apparent abandonment of the secret meetings in Harrington Street was a source of considerable anxiety and chagrin. I was particularly anxious about them. We had several of those who had taken part in the first meeting under close observation, but had learned nothing about them sufficient to justify our taking strong action. Most of them, indeed, seemed to be of the same apparently blameless type as Mr Mostyn Brown, and it was evident that if they were indeed enemy agents they had been selected or appointed by a master-hand at the game of espionage. And I wanted badly to gain some more information about them. Madame Gabrielle was ever on the alert, and soon it appeared from her report that the blind fiddler was expecting another raid. The ribbon bow on the parrot's cage changed to dark blue, and remained so for six days. On the seventh it was replaced by yellow. That night the old man remained in his room reading for hours after all the other inmates had retired. But that night no raid was made. I now began to think that it would be well if I took the mysterious Mostyn Brown under my own special observation. For a week during the moonless nights I shadowed him closely. I found out that he was a member of a certain third-class City club, frequented by a large number of "pure-blooded Englishmen" who happened to bear German names--of course they had been naturalised--and very soon my name appeared on the club books. It was not long before I managed to scrape acquaintance with Mostyn Brown over a game of billiards. I cultivated his friendship eagerly, and very soon we were on excellent terms. As a matter of fact, I wanted an invitation to his house, and at last I got it. I spent there one of the dullest evenings of my life, an evening, as it happened, entirely wasted. Beyond noting that the ribbon on the parrot's cage had again turned to blue, I saw nothing of the slightest interest. The next night, however, I made a discovery. Dropping in at the club, I found Mostyn Brown engaged in a game of billiards with a man whom I knew in the club as Harry Smith. A bullet-headed, bespectacled person, with hair standing erect as the bristles of a blacking brush, Smith looked the typical Hun, and I very soon decided in my own mind that Heinrich Schmidt was probably the name by which he was first known to the world. Suddenly a dispute arose about some point in the game, and in a moment words were running high. Half a dozen spectators noisily joined in the altercation, and the room was a Babel of dispute. I saw my chance.