It appears to have been in your family a good many years, Sir Eldred, for George Mansfield had previously come across a reference to it in one of his father's diaries, and his fertile brain now conceived the idea of using it in the process of carrying his scheme into effect. In the place of the Cupid he resolved to insert a miniature brazier containing the herbs and supplied with an electric fuse, the mechanism of which could be so contrived that whenever the clock should strike two, and two only, the dome would fly open, the brazier spring up, and the herbal preparation be ignited. He was only too well aware of the hereditary tendency of the Mansfield family to heart disease, and calculated that the shock of seeing so awful an apparition as the Arlakoo (which he firmly believed he could call up), together with the poisonous fumes that accompanied it--provided the door and windows were shut, which could be accomplished with the assistance of the Parrys--would encompass the deaths he desired. He chose, for his first victim, your mother. The day you and your father went to London to meet your brother, Parry smuggled George Mansfield into the house, and the latter, seizing an opportunity when your mother was out, fitted up the clock with the brazier containing the herbal preparation and the fuse. As you know, his diabolical scheme succeeded only too well, not only your mother, but your father and brother falling victims to it. This morning Mrs. Parry paid a visit to her son-in-law, and I overheard their conversation. Great surprise was expressed at the failure of the clock yesterday, and it was decided to try it again to-night. This is the result. The vapour you saw come out of the clock just now was a quite harmless gas which Mr. Craddock substituted for the original preparation George Mansfield had put there. We caught George nicely in the garden shortly after nine. We threatened to treat him in a thoroughly Bornean fashion"--and Vane produced his revolver--"and he then confessed everything. He is now in the safe custody of the C.I.D. men." "How did you come to suspect the clock, Vane?" I asked. "You forget the hole in the wall," he said, laughing. "I overheard continual allusion to the clock, and 'filling and charging' it again, and as I knew it was not customary to fill and charge clocks, I at once smelt a rat. My suspicions were confirmed when I came to your rescue last night and saw tiny spirals of the green vapour still emanating from the dome-shaped top. I consulted with Mr. Craddock, and with his assistance I was able to carry out this little plot which, I think, we will all agree has succeeded almost beyond expectation. Any more questions?"