The room had by that time become filled by a curious orange-coloured vapour--bright-orange--which to Ortmann's eyes was an extraordinary phenomenon. Had he not worn the protective mask he would have been instantly overwhelmed by an odour closely resembling that of cloves--a terribly fatal perfume, which would sweep away men like moths passing through the flame of a candle. "Well, my dear Drost," said the Count, "I know you will never rest until you've devised a means of carrying out our plans for the downfall of Merton Mansfield, and certainly you seem to have adopted some measure-- deadly though it may be--which is quite in accord with your ingenuity." He also spoke in a low, stifled voice from within his ugly mask. Drost nodded, and then into the marble mortar, in which he had mixed his devilish compounds, he poured something from a long blue glass-stoppered bottle, whereupon the place instantly became filled with volumes of grey smoke which, when it cleared, left the atmosphere perfectly clear--so clear, indeed, that both men removed their masks, sniffing, however, at the faint odour of cloves still remaining. Afterwards the old chemist took from the cupboard a small cardboard box which, on opening, contained, carefully packed in cotton wool, a short, stout, but hollow needle. Attached to it at one end was a small steel box about two inches broad and the same high. The box was perforated at intervals. "This is the little contrivance of which I spoke," said Drost gleefully, as he gazed upon it in admiration. "The explosive needle, when filled, and this little chamber, also properly charged, cannot fail to act." "I take it, my dear friend, that it will be automatic--eh?" remarked the Count, examining it with interest. Old Drost smiled, nodded, and replaced his precious contrivance in its box, after which both men left the laboratory, Drost carefully locking the door before descending the stairs to follow his companion. Both of them took a taxi to the fine house in Park Lane where Ortmann assumed the _role_ of society man. At ten o'clock a visitor was ushered in, and proved to be the young man whose real name was Schrieber. Apparently he had just returned from a journey, and had come straight from the station in order to make some secret report to Ortmann. When the three were closeted together the young German, who passed as a Swiss, produced from his pocket three small photographs showing the interior of a room taken from different angles, but always showing the fireplace. "Excellent!" declared Drost, as he examined all three prints beneath the strong light. "You have done splendidly." "Yes, all is in readiness. I have made friends with the maids, and when I return I shall be welcomed. No breath of suspicion will be aroused. We have now but to wait our time."