"Perfectly; they are also dangerous. To continue: On the night appointed—that is to say, as soon as we are all there—I am to administer to Harry a drug called metholycine. In all respects it is suitable for Mr. Francis's purpose, and a small dose produces within a very few minutes complete unconsciousness, to which, if no antidote or restorative is applied, succeeds death. It also is extremely volatile, more so even than aconite, and a very few hours after death no trace of it would be found in the stomach or other parts of the body. The drug, however, is exceedingly hard to get; no chemist would conceivably give it to any unauthorized person; but a few years ago I was experimenting with it, and it so happens that I still have some in my possession. Mr. Francis has a most retentive memory, and though I have no recollection of having ever mentioned this fact to him, he asked me this morning whether I had any left. He did so in so quiet and normal a voice that for the moment I was off my guard, and told him I had. But perhaps, after all, it was a lucky occurrence, for he seemed very much pleased, and played on his flute for a time. Then he came back to me and told me what I have already told you, and what I shall now tell you."

There was something strangely grim about the composure of the doctor's manner. You would have said he spoke of Danish politics; more grim, perhaps, was this mention of the flute-playing. Certainly it added an extreme vividness to his narrative, and the flute-player was more horrible than the man who planned death.

"In this respect, then, first of all," continued the icy voice, "I am useful to him. In the second place, Mr. Francis seems to have a singular horror of doing himself—actually, and with his hands—this deed. In another way also I shall be of service to him, and here I must touch on things more gruesome, but it is best that you should know all. The drug is to be administered late at night, after the servants are out of the way. It is almost completely without taste or odour, and Mr. Francis's suggestion is that a whisky and soda, which he tells me Harry always takes before going to bed, should be the vehicle. Ten minutes after he has taken it he will be unconscious, but he will live for another half hour. During that time we shall carry him down to the plate closet, where the Luck is kept with the rest of the plate; there Sanders will be. That part will be in Sanders's hands, but he will not use firearms, for fear of the noise of the report reaching the servants, and the blow that kills him, you understand, looking at the occurrence from the point of view of the coroner, must be dealt while he is still alive. Otherwise, the absence of effusion of blood and other details would show a doctor that he was already dead when his skull was broken—this is the idea—by a battering blow. Here, again, Mr. Francis anticipates that I shall be of use to him in determining when unconsciousness is quite complete, and death not yet immediate. He has a curiously strong desire that Harry should feel no pain, for he is very fond of him."

Lady Oxted and Geoffrey alike were glued to his words, both paler than their wont. As the doctor paused they sought each other's eyes, and found there horror beyond all speech.

"Some of the most valuable of the plate," continued the doctor, "will be taken, and, of course, the Luck. The plate will be the perquisite of Sanders; the Luck Mr. Francis will keep secretly, the presumption being that it was stolen also. Why, then, you may ask, should not Mr. Francis simply steal the Luck? For this reason: that as long as Harry lives it is his; on his death it becomes Mr. Francis's. Thus, morning will show the plate closet rifled, and Harry, clubbed to death, on the floor. The plan is complete and ingenious; indeed, it has no weak point. It will appear that Harry, after the servants had gone to bed, drank his whisky and soda, and, hearing something stirring, went downstairs. Finding the door of the plate closet open, he entered, and was instantly felled by a blow on the side of the head, which killed him. The burglars did not arouse any one else in the house, and escaped (even the details are arranged) by the same way as they entered—through the window of the gun room, which looks out, you are aware, on to the garden beds which adjoin the sweep of the carriage drive. Footprints of large, heavy boots will be found there; Mr. Francis bought a pair to-day at some cheap, ready-made shop."

Again, a horror palpable as a draught of cold air passed through the auditors, seeming to each to lift the hair upon the scalp. These trivial details of boots and flute-playing were of almost more intimate touch than the crime itself; they brought it at any rate into the range of realities, to the time of to-day or next week, to a familiar setting. Again the doctor spoke.

"I have already taken one precaution," he said. "I have emptied from its bottle the real metholycine and substituted common salt. I went to my house hurriedly, after seeing Mr. Francis, to get it, and I brought it away in my pocket. I shall be glad to dispose of it; it is not a thing to carry about."

He drew out a small packet, folded up with the precision of a dispensing chemist, and opened it. It contained an ounce of white coarse-grained powder, very like to ordinary salt, and, without more words, he emptied it on the fire. The red-hot coal blackened where he poured, then grew red again, and for a moment an aura of yellow flame flickered over the place.

"And Mr. Francis will not find it easy to get more," said the doctor.

The effect of this was great and immediate. Both Lady Oxted and Geoffrey felt as much relieved as if an imminent danger had been removed, though the logic of their relief, seeing that they both trusted Dr. Armytage, in whose domain the poison lay, was not capable of bearing examination. At any rate, Lady Oxted sat briskly up from the cramped huddling of the position in which she had listened to the doctor's story, and clapped her hands.