But in the moment of sighing Mr. Tertius reflected that there was no time for regret. It was a time—his time—for action; there was a thing to do which he wanted to do while he had the room to himself. Therefore he went to work, carefully and methodically. For a second or two he stood reflectively looking at the supper tray which still stood on the little table near the desk. With a light, delicate touch he picked up the glass which had been used and held it up to the light. He put it down again presently, went quietly out of the study to the dining-room across the hall, and returned at once with another glass precisely similar in make and pattern to the one which he had placed aside. Into that clear glass he poured some whisky, afterwards mixing with it some soda-water from the syphon—this mixture he poured away into the soil of a flower-pot which stood in the window. And that done he placed the second glass on the tray in the place where the first had stood, and picking up the first, in the same light, gingerly fashion, he went upstairs to his own rooms at the top of the house.

Five minutes later Mr. Tertius emerged from his rooms. He then carried in his hand a small, square bag, and he took great care to handle it very carefully as he went downstairs and into the square. At the corner of Orchard Street he got another taxi-cab and bade the driver go to Endsleigh Gardens. And during the drive he took the greatest pains to nurse the little bag on his knee, thereby preserving the equilibrium of the glass inside it.

Ringing the bell of one of the houses in Endsleigh Gardens, Mr. Tertius was presently confronted by a trim parlourmaid, whose smile was ample proof that the caller was well-known to her.

“Is the Professor in, Mary?” asked Mr. Tertius. “And if he is, is he engaged?”

The trim parlourmaid replied that the Professor was in, and that she hadn’t heard that he was particularly engaged, and she immediately preceded the visitor up a flight or two of stairs to a door, which in addition to being thickly covered with green felt, was set in flanges of rubber—these precautions being taken, of course, to ensure silence in the apartment within. An electric bell was set in the door; a moment or two elapsed before any response was made to the parlourmaid’s ring. Then the door automatically opened, the parlourmaid smiled at Mr. Tertius and retired; Mr. Tertius walked in; the door closed softly behind him.

The room in which the visitor found himself was a large and lofty one, lighted from the roof, from which it was also ventilated by a patent arrangement of electric fans. Everything that met the view betokened science, order, and method. The walls, destitute of picture or ornament, were of a smooth neutral tinted plaster; where they met the floor the corners were all carefully rounded off so that no dust could gather in cracks and crevices; the floor, too, was of smooth cement; there was no spot in which a speck of dust could settle in improper peace. A series of benches ran round the room, and gave harbourings to a collection of scientific instruments of strange appearance and shape; two large tables, one at either end of the room, were similarly equipped. And at a desk placed between them, and just then occupied in writing in a note-book, sat a large man, whose big muscular body was enveloped in a brown holland blouse or overall, fashioned something like a smock-frock of the old-fashioned rural labourer. He lifted a colossal, mop-like head and a huge hand as Mr. Tertius stepped across the threshold, and his spectacled eyes twinkled as their glance fell on the bag which the visitor carried so gingerly.

“Hullo, Tertius!” exclaimed the big man, in a deep, rich voice. “What have you got there? Specimens?”

Mr. Tertius looked round for a quite empty space on the adjacent bench, and at last seeing one, set his bag down upon it, and sighed with relief.

“My dear Cox-Raythwaite!” he said, mopping his forehead with a bandanna handkerchief which he drew from the tail of his coat. “I am thankful to have got these things here in—I devoutly trust!—safety. Specimens? Well, not exactly; though, to be sure, they may be specimens of—I don’t quite know what villainy yet. Objects?—certainly! Perhaps, my dear Professor, you will come and look at them.”

The Professor slowly lifted his six feet of muscle and sinew out of his chair, picked up a briar pipe which lay on his desk, puffed a great cloud of smoke out of it, and lounged weightily across the room to his visitor.