The sealed room

"A solicitor of an active habit and athletic tastes who is compelled by his hopes of business to remain within the four walls of his office from ten till five must take what exercise he can in the evenings. Hence it was that I was in the habit of indulging in very long nocturnal excursions, in which I sought the heights of Hampstead and Highgate in order to cleanse my system from the impure air of Abchurch Lane. It was in the course of one of these aimless rambles that I first met Felix Stanniford, and so led up to what has been the most extraordinary adventure of my lifetime."