On the fourth day I noticed a slight fact. The ring on the top of the parrot's cage was tied with a big bow of yellow ribbon. Three days later it was altered to dark blue. On the eighth day it had returned to yellow again. Why these changes? Were they signals? That night enemy aircraft crossed the south-east coast, but their attempts to reach London were defeated by the terrific fire of the anti-aircraft guns and by a swift concentration of our fighting aeroplanes, which broke up several successive squadrons, and sent the raiders hurrying home again. Several of my capable assistants then took over the task of finding out all that was known regarding the house in Lembridge Square. Forty-eight hours later I had a full report. I learned that the man in whose room the parrot lived was one of the mysterious band who foregathered to meet Kristensten in the empty house in Harrington Street. He was then dressed as a special constable, a part which, by the way, he had no right whatever to play. He bore the thoroughly English name of Mostyn Brown, and was in business in the City as the agent of a Manchester firm of cotton merchants. Apart from the fact of his presence that night in Harrington Street, nothing that the most exhaustive inquiries revealed suggested in the smallest degree any association with agents of the enemy. To all appearances he was a perfectly respectable City man, in no way different from thousands of others. But--there was a very big but: what was his business in the dead of night in an empty house in the West End in company of a suspected German spy? A few days later the men who were keeping the houses in Lembridge Square and Hereford Road under surveillance sent me a strange report, which set me thinking deeply. By some means--whether he suspected he was being watched or whether a lucky chance favoured him, we never knew--Blind Heinrich managed to elude the unwearying vigilance of Madame Gabrielle and arrived alone, evidently in a hurry, at Westbourne Grove. Here he hailed a taxi and was driven to Waterloo Station. There at the booking-office on the loop-line side he had met a short, fat man, to whom, after a brief conversation, he handed a bottle wrapped in white paper. They remained in conversation a few minutes longer and then parted. The fat man was followed to the tube railway and thence to King's Cross, where he had bought a ticket for Peterborough, and left by the five-thirty express.