"He will be sure to drink that," he said, as he replaced the glass within easy reach of the sofa; and then removing the stopper from the blue bottle he held, replaced it partly in the neck, rested it upon the edge of the steaming glass, and began to count the drops which fell. One--two--three. Each drop at an interval after the one which had preceded it, while with his left hand he steadied the tumbler. As the third drop fell into the glass there was a strange noise outside--a dull scuffling of feet, mutterings of voices, and then a low imperious tapping on the panel of the door. At the first sound the doctor turned his head sharply and gazed in the direction of the door, while the rest of his body seemed to have become fixed in a cataleptic state, save that his eyes dilated and his jaw dropped. And meanwhile, slowly and steadily, drip--drip--drip--drip, the globules of fluid fell from the tip of the blue bottle into the steaming glass at last in quite a stream. A strange dread had overcome the doctor. His patient's words about his diamonds had proved to be true; were the rest, then, true--that he had been pursued by men whose aim it was to plunder, perhaps murder him, and they had really traced him down here? "Bah! am I turning childish?" said the doctor, starting up, and letting the stopper fall back into its place in the bottle, just as his patient moaned slightly, turned impatiently in his sleep, and the ulster glided to the floor. The doctor stooped quickly, raised it, and threw it over his patient, and, as he bent over him, listened intently to the repetition of the tapping. "It might be," he said softly. "Pish! absurd! The wanderings of a diseased mind." Catching up the bottle from where he had placed it on the table, he walked quickly towards the door, paused, returned, and stooped as if to pick up the poker. Then smiled at his folly. He passed softly out of the door, and closed it after him, to go to the shelves in the dark, where he made a clicking noise among the bottles, as he reached up; for there in the darkness the feeling once more assailed him that his patient might be right, while for the third time, more plainly heard now, there came a sharp tapping. The doctor crossed to the gas bracket, turned it up, and as its light filled the surgery, he walked boldly to the lobby-door, opened it, and the dull red glare from the fanlight over the outer door shone upon his handsome placid face. The next moment he had opened the outer door, and was gazing at a group of three men. Mark Heath's announcement flashed through his brain once more, and then gave place to the ideas furnished by his visitors. "Thought you were a-bed. Couldn't find the bell. This cursed fog, sir. Our friend here knocked down by a cab, and we saw your red light as we were trying to get him to our hotel." "Tut, tut, tut!" ejaculated the doctor. "Bring him in, gentlemen."