I went to my bedroom and followed his advice. When I returned with the pistol the table had been cleared, and Holmes was engaged in his favourite occupation of scraping upon his violin.

“The plot thickens,” he said, as I entered; “I have just had an answer to my American telegram. My view of the case is the correct one.”

“And that is?” I asked eagerly.

“My fiddle would be the better for new strings,” he remarked. “Put your pistol in your pocket. When the fellow comes speak to him in an ordinary way. Leave the rest to me. Don’t frighten him by looking at him too hard.”

“It is eight o’clock now,” I said, glancing at my watch.

“Yes. He will probably be here in a few minutes. Open the door slightly. That will do. Now put the key on the inside. Thank you! This is a queer old book I picked up at a stall yesterday—‘De Jure inter Gentes’—published in Latin at Liege in the Lowlands, in 1642. Charles’ head was still firm on his shoulders when this little brown-backed volume was struck off.”

“Who is the printer?”

“Philippe de Croy, whoever he may have been. On the fly-leaf, in very faded ink, is written ‘Ex libris Guliolmi Whyte.’ I wonder who William Whyte was. Some pragmatical seventeenth century lawyer, I suppose. His writing has a legal twist about it. Here comes our man, I think.”

As he spoke there was a sharp ring at the bell. Sherlock Holmes rose softly and moved his chair in the direction of the door. We heard the servant pass along the hall, and the sharp click of the latch as she opened it.

“Does Dr. Watson live here?” asked a clear but rather harsh voice. We could not hear the servant’s reply, but the door closed, and some one began to ascend the stairs. The footfall was an uncertain and shuffling one. A look of surprise passed over the face of my companion as he listened to it. It came slowly along the passage, and there was a feeble tap at the door.

“Come in,” I cried.

At my summons, instead of the man of violence whom we expected, a very old and wrinkled woman hobbled into the apartment. She appeared to be dazzled by the sudden blaze of light, and after dropping a curtsey, she stood blinking at us with her bleared eyes and fumbling in her pocket with nervous, shaky fingers. I glanced at my companion, and his face had assumed such a disconsolate expression that it was all I could do to keep my countenance.