The following morning I found Kennedy up ahead of me, and I felt certain that he had gone to the laboratory. Sure enough, I found him at work in the midst of the innumerable scientific devices which he had gathered during years of crime detection of every sort.

As usual, he was surrounded by a perfect litter of test tubes, beakers, reagents, microscopes, slides, and culture tubes. He had cut out the curious spots from the towel I had discovered and was studying them to determine their nature. From the mass of paraphernalia I knew he was neglecting no possibility which might lead to the hidden truth or produce a clue to the crime.

"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.

"If the towel wasn't used to clean the fatal needle," I went on, "then it may have been used before they went out instead of afterward."

"Exactly. As a matter of fact, if I had not been so confused yesterday by all the details of the case, by the many people involved, I would have noticed at a glance that the blood spots on the towel could not come from some one using it to wipe the needle. And any hypothesis that it had been used out in Tarrytown was ridiculous, because Miss Lamar was only scratched faintly and lost no blood. If I had been a little more clever I might have been altogether too clever. I might possibly have thrown the towel away, because there certainly was no logical reason for connecting it with the crime."

"Just when do you suppose Stella was pricked?" I asked.

"That's a vital consideration. Just now I do not know the poison and so cannot tell how quickly it acted." He began to put aside his various paraphernalia. "Suppose we go at this thing by a process of deduction rather than from the end of scientific analysis." He sat on a corner of the bench. "What do we find?" he began.

"While I've been working here with the test tubes and the microscope I've been trying to reconstruct what must have happened, trying to trace out every action of Stella Lamar as nearly as it is possible for us to do so. I don't think we need to go back of their arrival at the house, for the present. They seem to have been there a long while before the taking of the particular scene, since there were twelve other scenes preceding and since it requires time to put up the electric lights and make the connections, as well as to set the cameras, take tests, rearrange the furniture, and all the rest of it.

"They arrived at the house in two automobiles; with the exception of Phelps, who was there already, and Manton, who came in his own limousine. That means that Miss Lamar had company on the trip out, the principals probably riding with each other in one car. At the house they were all more or less together. There were people about constantly and it would seem as if there was small opportunity for anyone to inflict the scratch which caused her death. I don't mean that it would have been impossible to prick her. I mean that she would have felt the jab of the point. In all likelihood she would have cried out and glanced around. Take a needle yourself, sometime, Walter, and try to duplicate the scratch on your own arm in such a way that you would not be aware of it.

"So you see I'm counting upon some sort of exclamation from Miss Lamar. If she were inoculated with the poison with other folks about, it is sure some one would have remembered a cry, a questioning glance, a quick grasp of the forearm—for the nerves are very sensitive in the skin there—"

"No one did recall anything of the kind," I interrupted.

"It is from that fact that I hope to deduce something. Now let's follow her, figuratively, to her little dressing room. This was a part of the living room where the rest waited. It is not a certainty, but yet rather a sure guess, that if she had received a scratch behind those thin silk curtains her cry would have been heard. What is even more plausible is that she would have hurried out, or at least put her head out, to see who had pricked her.

"I made a very careful examination of that little alcove with the idea that some artifice might have been used. It occurred to me that a poisoned point could have been inserted in her belongings in some way so that she would have brought about her own death, directly. To have caught herself on a needle point in her bag, for instance, would not have impressed her to the point of making a disturbance. She might have checked her exclamation, in that case, because she would be blaming herself.

"But I found nothing in her things, nor did I discover anything in the library. It seems to me, therefore, that we must look for a direct human agency."

A thought struck me and I hastened to suggest it. "Could some device have been arranged in her clothes, Craig; something like the poison rings of the Middle Ages, a tiny metal thing to spring open and expose its point when pressed against her in the action of the scenes?"

"That occurred to me at the time. That's why I asked Mackay to send all her clothes down here, every stitch and rag of them. I've gone over everything already this morning. Not only have I examined the various materials for stains, but I've tested each hook and eye and button and pin. I've been very careful to cover that possibility."

"You think, then, she was scratched deliberately by some one during the taking of the scenes?"

"If you've followed my line of reasoning you will see that we are driven to that assumption. Perhaps later I will make tests on a given number of girls of Stella's general age and type and temperament to show that they will cry out at the unexpected prick of a fine needle. It's illogical to expect that a cry from Miss Lamar, even an exclamation, would have passed unnoticed except during the excitement of actual picture taking."

Another inspiration came to me, but I was almost afraid to voice it. It seemed a daring theory. "Could death have resulted from poison administered in some other fashion, by something she had eaten, for instance?" I ventured. "Couldn't the scratch be coincidental?"

Kennedy shook his head. "There's the value of our chemical analysis and scientific tests. Her stomach contents showed nothing except as they might have been affected by her weakened condition. From Doctor Blake's report—and he found no ordinary symptoms, remember—and from my own observation, too, I can easily prove in court that she was killed by the mark which was so small that it escaped the physician altogether."

I turned away. Once more Kennedy's reasoning seemed to be leading into a maze of considerations beyond me. How could the deductive method produce results in a case as mysterious as this?

"Having determined that Miss Lamar received the inoculation during the making of one of the scenes, as nearly as we can do so," Kennedy went on, "suppose we take the scenes in order, one at a time, from the last photographed to the first, analyzing each in turn. Remember that we seek a situation where there is not only an opportunity to jab her with a needle, but one in which an outcry would be muffled or inaudible."

I now saw that Kennedy had brought in the bound script of the story, "The Black Terror," and I wondered again, as I had often before, at his marvelous capacity for attention to detail.

"'The spotlight on the floor reveals the girl sobbing over the body of the millionaire,'" he read, aloud, musingly. "H'mm! 'She screams and cries out.' Then the others rush in."

For several moments Kennedy paced the floor of the laboratory, the manuscript open in his hands.

"We rehearsed that, with Werner; and we questioned everyone, too. And remember! Miss Lamar, instead of crying out as she was supposed to do, just crumpled up silently. So"—thumbing over a page—"we work back to scene twelve. She—she was not in that at all. Scene eleven—"

Slowly, carefully, Kennedy went through each scene to the beginning. "Certainly a dramatic opening for a mystery picture," he remarked, suddenly, as though his mind had wandered from his problem to other things. "We must admit that Millard can handle a moving-picture scenario most beautifully."

Whether it was professional jealousy or the thought of Enid, rather than the memory of my own poor attempts at screen writing, I certainly was in no mood to agree with Kennedy, for all that I knew he was correct.

"Here!" He thrust the binder in my hands. "Read that first scene," he directed. "Meanwhile I am going to phone Mackay to make sure he has had the house guarded and to make double sure no one goes near the library. We're going out to Tarrytown again, Walter, and in the biggest kind of hurry."

"What's the idea, Craig?" Kennedy's occasional bursts of mysteriousness, characteristic of him and often necessary when his theories were only half formed and too chaotic for explanations, always piqued me.

He did not seem to hear. Already he was at the telephone, manipulating the receiver hook impatiently. "What a dummy I am!" he exclaimed, with genuine feeling. "What—what an awful dummy!"

Knowing I would get nothing out of him just yet, I turned to the scene, reading as he told me. At first I could not see where the detail concerned Stella Lamar in any way. Then I came to the description of her introductory entrance, the initial view of her in the film. The lines of typewriting suddenly stood out before me in all their suggestive clearness.

The spotlight in the hands of a shadowy figure roves across the wall and to the portieres. As it pauses there the portieres move and the fingers of a girl are seen on the edge of the silk. A bare and beautiful arm is thrust through almost to the shoulder and it begins to move the portieres aside, reaching upward to pull the curtains apart at the rings.

"You think there's something about the portieres—" I began.

Then I saw that Kennedy had his connection, that something disturbed him, that some intelligence from the other end had caught him by surprise.

"You say you were just trying to get me, Mackay? You've something to tell me and you want me to come right out—you have summoned Phelps and he's on his way from the city also—?"

"What happened?" I asked, as Kennedy hung up.

"I don't know, Walter. Mackay said he didn't want to talk over the phone and that we had just time to catch the express."

"But—"

"Hurry!" He glanced about as if wondering whether any of his scientific instruments would help him.