In response to his ring at the visitors' bell, a tall, middle-aged, round-faced manservant opened the door. "Is Dr Jerrold in?" Jack inquired. "Yes, sir," was the man's quick reply; and then, as Sainsbury entered, he added politely: "Nice evening, sir." "Very," responded the visitor, laying-down his hat and stick and taking off his overcoat in the wide, old-fashioned hall. Dr Jerome Jerrold, though still a young man, was a consulting physician of considerable eminence, and, in addition, was Jack's most intimate friend. Their fathers had been friends, living in the same remote country village, and, in consequence, ever since his boyhood he had known the doctor. Jack was a frequent visitor at the doctor's house, Jerrold always being at home to him whenever he called. The place was big and solidly furnished, a gloomy abode for a bachelor without any thought of marrying. It had belonged to Jerrold's aunt, who had left it to him by her will, together with a comfortable income; hence her nephew had found it, situated as it was in the centre of the medical quarter of London, a most convenient, if dull, place of abode. On the ground floor was the usual depressing waiting-room, with its big round table littered with illustrated papers and magazines; behind it the consulting-room, with its businesslike writing-table--whereon many a good man's death-warrant had been written in that open case-book--its heavy leather-covered furniture, and its thick Turkey carpet, upon which the patient trod noiselessly. Above, in the big room on the first floor, Jerome Jerrold had his cosy library--for he was essentially a studious man, his literary mind having a bent for history, his "History of the Cinquecento" being one of the standard works upon that period. Indeed, while on the ground floor all was heavy, dull and gloomy, well in keeping with the dismal atmosphere which all the most famous West-End doctors seem to cultivate, yet, on the floor above, one passed instantly into far brighter, more pleasant and more artistic surroundings. Without waiting for the servant, Thomasson, to conduct him upstairs, Jack Sainsbury ran lightly up, as was his habit, and tried the door of the doctor's den, when, to his surprise, he found it locked. He twisted the handle again, but it was certainly firmly fastened. "Jerome!" he cried, tapping at the door. "Can I come in? It's Jack!" But there was no reply. Sainsbury strained his ears at the door, but could detect no movement within. A taxicab rushed past; then a moment later, when the sound had died away, he cried again-- "Jerome! I'm here! I want to see you, old fellow. Open the door." Still there was no answer. Thomasson, standing at the foot of the wide, old-fashioned stairs, heard his master's visitor, and asked-- "Is the door locked, sir?" "Yes," Jack shouted back.