"Naturally, having discovered this, we gave instructions for a keener watch than ever to be kept on both these men. But the name of the German chemist gave me personally a new and most important clue. There had been employed at the Waldorf Hotel, for some weeks up to the end of the first week in May, a German-Swiss young man, who then called himself Ebers. He acted as valet to several residents; amongst others, Mr. Fullaway. He was often in and out of Mr. Fullaway's rooms. Once, Mr. Fullaway being out, and I having nothing to do, I was cleaning up some photographic apparatus which I had there. This man Ebers came in with some clothes of Mr. Fullaway's. Seeing what I was doing, he got talking to me about photography, saying that he himself was an amateur. He recommended to me certain materials and things of that sort which he said he could get from a friend of his, a chemist, who was an enthusiastic photographer and manufactured chemicals and things used in photography. I gave him some money to get me a supply of things, and he brought various packets and parcels to me two or three days later. Each packet bore the name of Otto Schmall, and an address in a street which runs off Mile End Road. "Now, when the private inquiry agent made his reports to Mr. Rayner and myself about Van Koon, and told us where he had been tracked to more than once, I, of course, remembered the name of Schmall, and Mr. Rayner and I began to put certain facts together. They were these: "_First._--Ebers had easy access to Mr. Fullaway's room at all hours, and was often in them when both Mr. Fullaway and I were out. Mr. Fullaway is notoriously careless in leaving papers and documents, letters and telegrams lying around. Ebers had abundant opportunities of reading lots of documents relating to (1) the Pinkie Pell pearls, and (2) the proposed Nastirsevitch deal. "_Second._--Ebers was a friend of Schmall. Schmall was evidently a man of great cleverness in chemistry. "_Third._--All the circumstances of Mr. James Allerdyke's death, and of Lisette Beaurepaire's death, pointed to unusually skillful poisoning. Who was better able to engineer that than a clever chemist? "_Fourth._--The jewels belonging to the Princess Nastirsevitch had undoubtedly fallen into Van Koon's hands. Van Koon was a friend of Schmall. So also, evidently, was Merrifield. Now, Merrifield, as Delkin's secretary, knew of the proposed deal.