“Thank you,” said Holmes, shutting his eyes; “pray go on.”

“I did exactly what he indicated and waited until the other clerks had departed. One of them in my room, Charles Gorot, had some arrears of work to make up, so I left him there and went out to dine. When I returned he was gone. I was anxious to hurry my work, for I knew that Joseph - the Mr. Harrison whom you saw just now - was in town, and that he would travel down to Woking by the eleven-o’clock train, and I wanted if possible to catch it.

“When I came to examine the treaty I saw at once that it was of such importance that my uncle had been guilty of no exaggeration in what he said. Without going into details, I may say that it defined the position of Great Britain towards the Triple Alliance, and foreshadowed the policy which this country would pursue in the event of the French fleet gaining a complete ascendency over that of Italy in the Mediterranean. The questions treated in it were purely naval. At the end were the signatures of the high dignitaries who had signed it. I glanced my eyes over it, and then settled down to my task of copying.

“It was a long document, written in the French language, and containing twenty-six separate articles. I copied as quickly as I could, but at nine o’clock I had only done nine articles, and it seemed hopeless for me to attempt to catch my train. I was feeling drowsy and stupid, partly from my dinner and also from the effects of a long day’s work. A cup of coffee would clear my brain. A commissionaire remains all night in a little lodge at the foot of the stairs and is in the habit of making coffee at his spirit-lamp for any of the officials who may be working overtime. I rang the bell, therefore, to summon him.

“To my surprise, it was a woman who answered the summons, a large, coarse-faced, elderly woman, in an apron. She explained that she was the commissionaire’s wife, who did the charing, and I gave her the order for the coffee.

“I wrote two more articles, and then, feeling more drowsy than ever, I rose and walked up and down the room to stretch my legs. My coffee had not yet come, and I wondered what the cause of the delay could be. Opening the door, I started down the corridor to find out. There was a straight passage, dimly lighted, which led from the room in which I had been working, and was the only exit from it. It ended in a curving staircase, with the commissionaire’s lodge in the passage at the bottom. Halfway down this staircase is a small landing, with another passage running into it at right angles. This second one leads by means of a second small stair to a side door, used by servants, and also as a short cut by clerks when coming from Charles Street. Here is a rough chart of the place.”

“Thank you. I think that I quite follow you,” said Sherlock Holmes.

“It is of the utmost importance that you should notice this point. I went down the stairs and into the hall, where I found the commissionaire fast asleep in his box, with the kettle boiling furiously upon the spirit-lamp. I took off the kettle and blew out the lamp, for the water was spurting over the floor. Then I put out my hand and was about to shake the man, who was still sleeping soundly, when a bell over his head rang loudly, and he woke with a start.

“ ‘Mr. Phelps, sir!’ said he, looking at me in bewilderment.

“ ‘I came down to see if my coffee was ready.’

“ ‘I was boiling the kettle when I fell asleep, sir.’ He looked at me and then up at the still quivering bell with an ever-growing astonishment upon his face.

“ ‘If you was here, sir, then who rang the bell?’ he asked.

“ ‘The bell!’ I cried. ‘What bell is it?’

“ ‘It’s the bell of the room you were working in.’