He spent nearly three-quarters of an hour taking a bearing based upon the problematical position of the lights, the height and density of the box screen and then boldly and rapidly opened the door, stepped through and closed it behind him. His calculations had been accurate. He found himself in a room, the extent of which he could only conjecture. What, however, interested him mostly was the accuracy of his calculation that the door was hidden. An "L"-shaped stack of crates was piled within two feet of the ceiling, and formed a little lobby to anybody entering the vault the way Beale had come. They were stacked neatly and methodically, and with the exception of two larger packing-cases which formed the "corner stone" the barrier was made of a large number of small boxes about ten inches square.
There was a small step-ladder, evidently used by the person whose business it was to keep this stack in order. Beale lifted it noiselessly, planted it against the corner and mounted cautiously.
He saw a large, broad chamber, its groined roof supported by six squat stone pillars. Light came not only from mercurial lamps affixed to the ceiling, but from others suspended above the three rows of benches which ran the length of the room.
Mercurial lamps do not give a green light, as he knew, but a violet light, and the green effect was produced by shades of something which Beale thought was yellow silk, but which he afterwards discovered was tinted mica.
At intervals along the benches sat white-clad figures, their faces hidden behind rubber masks, their hands covered with gloves. In front of each man was a small microscope under a glass shade, a pair of balances and a rack filled with shallow porcelain trays. Evidently the work on which they were engaged did not endanger their eyesight, for the eye-pieces in the masks were innocent of protective covering, a circumstance which added to the hideous animal-like appearance of the men. They all looked alike in their uniform garb, but one figure alone Beale recognized. There was no mistaking the stumpy form and the big head of the Herr Professor, whose appearance in Oliva Cresswell's room had so terrified that young lady.
He had expected to see him, for he knew that this old German, poverty-stricken and ill-favoured, had been roped in by van Heerden, and Beale, who pitied the old man, had been engaged for a fortnight in trying to worm from the ex-professor of chemistry at the University of Heidelberg the location of van Heerden's secret laboratory. His efforts had been unsuccessful. There was a streak of loyalty in the old man, which had excited an irritable admiration in the detective but had produced nothing more.
Beale's eyes followed the benches and took in every detail. Some of the men were evidently engaged in tests, and remained all the time with their eyes glued to their microscopes. Others were looking into their porcelain trays and stirring the contents with glass rods, now and again transferring something to a glass slide which was placed on the microscope and earnestly examined.
Beale was conscious of a faint musty odour permeating the air, an indescribable earthy smell with a tang to it which made the delicate membrane of the nostrils smart and ache. He tied his handkerchief over his nose and mouth before he took another peep. Only part of the room was visible from his post of observation. What was going on immediately beneath the far side of the screen he could only conjecture. But he saw enough to convince him that this was the principal factory, from whence van Heerden was distilling the poison with which he planned humanity's death.
Some of the workers were filling and sealing small test-tubes with the contents of dishes. These tubes were extraordinarily delicate of structure, and Beale saw at least three crumble and shiver in the hands of the fillers.
Every bench held a hundred or so of these tubes and a covered gas-jet for heating the wax. The work went on methodically, with very little conversation between the masked figures (he saw that the masks covered the heads of the chemists so that not a vestige of hair showed), and only occasionally did one of them leave his seat and disappear through a door at the far end of the room, which apparently led to a canteen.