"My dear Eva,--I could not come to-day, but shall be there this evening. Everything is complete. When the truth becomes known the discovery will, I anticipate, startle the world. It must, for reasons you know, remain a strict secret. Do not breathe a word to a soul.--Yours ever. "Anna." "That may refer to the invention we found in the laboratory; a scientific discovery which no one has come forward to claim. But who, I wonder, is Anna?" "She might be the dead woman," Boyd suggested. "True," I agreed. "So she might." During fully half an hour we still remained in that small cosy boudoir, which seemed to be Eva's own room, examining everything carefully and taking the utmost precaution to replace everything exactly as we found it. In this Boyd displayed real genius. Whatever was moved he rearranged it with an exactness little short of astounding. His astuteness was remarkable. Nothing escaped him, now that he was on the trail. Yet, as I wandered about, examining things here and there, I could not repress a feeling of reproach, for had I not, after all, assisted in this secret search which had resulted so disastrously for the strange, mysterious woman I so dearly loved? She was now under the suspicion of the police. They would keep her under surveillance, for the evidence we had already obtained was sufficient to induce any magistrate to grant a warrant for her arrest. A sudden sense of a vast, immeasurable loss fell upon me. The small box containing the greyish-blue powder had been replaced in the concealed drawer, and everything had been rearranged in the room, when the local officer said-- "At the end of the corridor there's another sitting-room." "Very well," Boyd answered. "Let's see what it's like," and we all three, lights in hand, followed our guide until we entered a smaller sitting-room. An easel stood in it and it was apparently used by Eva as a studio, for she, I knew, took lessons in painting. Upon the easel stood a canvas half finished, while near the window was a small writing-table, the one long drawer of which was locked. The lock was a common one and quickly yielded to Boyd's skeleton keys, but within we only found another collection of old letters, a quantity of pencil sketches, colours and other odds and ends connected with her art studies. Boyd was turning them over methodically, when suddenly an involuntary exclamation escaped him. "Ah! What's this?" he ejaculated, at the same time drawing forth a card about the size of a lady's visiting card, and held it out to me. Upon it was drawn in ink a circle. It was executed in exactly the same manner as that we had found concealed beneath the plates in the dining-room at Phillimore Place. Again he turned the things over and drew out three or four other cards of similar size and style, each bearing a device, one having upon its face the straight line exactly like that we had found in Kensington. "You recognise these devices?" he inquired.