Holmes and I put on our dress-clothes, so that we might appear to be two theatre-goers homeward bound.  In Oxford Street we picked up a hansom and drove to an address in Hampstead.  Here we paid off our cab, and with our great coats buttoned up, for it was bitterly cold, and the wind seemed to blow through us, we walked along the edge of the heath.

“It’s a business that needs delicate treatment,” said Holmes.  “These documents are contained in a safe in the fellow’s study, and the study is the ante-room of his bed-chamber.  On the other hand, like all these stout, little men who do themselves well, he is a plethoric sleeper.  Agatha—­that’s my fiancee—­says it is a joke in the servants’ hall that it’s impossible to wake the master.  He has a secretary who is devoted to his interests, and never budges from the study all day.  That’s why we are going at night.  Then he has a beast of a dog which roams the garden.  I met Agatha late the last two evenings, and she locks the brute up so as to give me a clear run.  This is the house, this big one in its own grounds.  Through the gate—­now to the right among the laurels.  We might put on our masks here, I think.  You see, there is not a glimmer of light in any of the windows, and everything is working splendidly.”

With our black silk face-coverings, which turned us into two of the most truculent figures in London, we stole up to the silent, gloomy house.  A sort of tiled veranda extended along one side of it, lined by several windows and two doors.

“That’s his bedroom,” Holmes whispered.  “This door opens straight into the study.  It would suit us best, but it is bolted as well as locked, and we should make too much noise getting in.  Come round here.  There’s a greenhouse which opens into the drawing-room.”

The place was locked, but Holmes removed a circle of glass and turned the key from the inside.  An instant afterwards he had closed the door behind us, and we had become felons in the eyes of the law.  The thick, warm air of the conservatory and the rich, choking fragrance of exotic plants took us by the throat.  He seized my hand in the darkness and led me swiftly past banks of shrubs which brushed against our faces.  Holmes had remarkable powers, carefully cultivated, of seeing in the dark.  Still holding my hand in one of his, he opened a door, and I was vaguely conscious that we had entered a large room in which a cigar had been smoked not long before.  He felt his way among the furniture, opened another door, and closed it behind us.  Putting out my hand I felt several coats hanging from the wall, and I understood that I was in a passage.  We passed along it and Holmes very gently opened a door upon the right-hand side.  Something rushed out at us and my heart sprang into my mouth, but I could have laughed when I realized that it was the cat.  A fire was burning in this new room, and again the air was heavy with tobacco smoke.  Holmes entered on tiptoe, waited for me to follow, and then very gently closed the door.  We were in Milverton’s study, and a portiere at the farther side showed the entrance to his bedroom.