True, she had sounded me as to what undertaking I was ready to give, but the whole situation was so horrible and so bewildering that I could not bring myself to make any compact that would prevent Greer's assassin being exposed. So, instead, I sat full of chagrin, telling the pair much which held them in fear and apprehension. It was evident that I knew more than they had believed I did, and that Langton was filled with regret that he had invited me there. What, I wondered, could possibly be Ethelwynn's motive in concealing her father's death? I recollected how the assassin must have brushed past her in the Red Room to enter the laboratory on that fatal night, and that he must have again passed her on leaving. Did she awake and recognise him, or had she herself been an accomplice in securing her father's sudden and tragic end? Who could tell? In that startling suggestion I found much food for deep reflection. CHAPTER TWENTY SIX. I SCENT THE IMPOSTOR. A whole fortnight went past. Mabel's silence was inexplicable. The house in Sussex Place was still in the hands of the caretaker, and, though I watched both Doctor Flynn and Leonard Langton in secret, the results of my vigilance were nil. I was in despair. Refused assistance by Scotland Yard, and treated as an enemy by Kershaw Kirk, I could only sit with Gwen at home and form a thousand wild conjectures. Advertisements for news of Mabel had brought no word of response. Indeed, it seemed much as though the theory of those two detectives was the correct one, namely, that she had left me of her own will, and did not intend to return. Gwen, indeed, suggested this one day, but I made pretence of scouting it. Mabel's mother, who now lived up in Aberdeenshire, had written two letters, and I had been compelled to reply, to tell a lie and say that she was away at Cheltenham. My business I neglected sadly, for nowadays I seldom went to the garage. Kirk was, I understood, living in Whitehall Court, but I did not call upon him. What was the use? I had tried every means of learning where Mabel was, but, alas! there seemed a conspiracy of silence against me. I had left no effort unexerted. Yet all had been in vain. Antonio had, according to Ethelwynn, joined "the Professor" in Hungary. Was not that, in itself, sufficient evidence of collusion? As for Pietro, inquiry I made in the Euston Road showed that he had not yet returned to England. Many times I felt impelled to go out to Buda-Pesth and endeavour to trace the pair. But I hesitated, because, finding Ethelwynn's statements unreliable in some particulars, I feared to accept what she said as the truth. Would it not be to her interest to mislead me and send me off upon a wild-goose chase?