In company we walked to Leman Street Police Station, one of the chief centres of the Metropolitan Police in the East End, and there, in an upper office, Ambler had a long consultation with the sergeant of the Criminal Investigation Department. I described the appearance of the body, and stated my suspicions of poisoning, all of which the detective carefully noted before going forth to make his own examination. My address was taken, so that I might assist at the post-mortem, and then, shortly after midnight I drove back westward through the City with Ambler at my side. He spoke little, and when in Oxford Street, just at the corner of Newman Street, he descended, wished me a hurried good-night, and disappeared into the darkness. He was often given to strange vagaries of erratic movement. It was as though some thought had suddenly occurred to him, and he acted at once upon it. That night I scarcely closed my eyes. My brain was awhirl with thoughts of all the curious events of the past few months--the inexplicable presence of old Mr. Courtenay, and the subsequent death of Mary and of the only man who, according to Ambler, knew the remarkable secret. Ethelwynn's strange words worried me. What could she mean? What did she know? Surely hers could not be a guilty conscience. Yet, in her words and actions I had detected that cowardice which a heavy conscience always engenders. One by one I dissected and analysed the Seven Secrets, but not in one single instance could I obtain a gleam of the truth. While at the hospital next day I was served with a notice to assist at the post-mortem of the unfortunate Lane, whose body was lying in the Shadwell mortuary; and that same afternoon I met by appointment Doctor Tatham, of the London Hospital, who, as is well known, is an expert toxicologist.