“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.