"Have you learned anything yet?" I asked.
"Those brownish spots were blood, of course," was his reply as he stopped a moment in his work. "In the blood I discovered some other substance, though I can't seem to identify it yet. It will take time. I thought it might be a drug or poison, but it doesn't seem to be—at least nothing one might ordinarily expect."
"How about the other spots, not the Chinese yellow?"
"Another problem I haven't solved. I dissolved enough of them so that I have plenty of material to study if I don't waste it. But so far I haven't been able to identify the substance with anything I know. There's a lot more work of elimination, Walter, before we're on the road to the solution of this case. Whatever stained the towel was very unusual. As near as I can make out the spots are of some protein composition. But it's not exactly a poison, although many proteins may be extremely poisonous and extremely difficult to identify because they are of organic nature."
I was disappointed. It seemed to me that he had made comparatively little progress so far.
"There's one thing," he added. "Samples of the body fluids of the victim have been sent down by the coroner at Tarrytown and I have analyzed them. While I haven't decided what it was that killed Stella Lamar, I am at least convinced that it has something to do with these towel spots. They are not exactly the same—in fact, I should say they were complementary, or, perhaps better, antithetical."
"The mark wasn't made by the needle which scratched her, then?"
"That's what I thought at first, that the point used had been wiped off on the towel. Then I decided that the spots had nothing to do with the case at all. Now I believe there is some connection, after all."
"I—I don't understand it," I protested.
"It's very baffling," he agreed, absent-mindedly.