“In both cases the selection of the poison was suited to the conditions.  Therefore, if an attempt was made to kill Shirley—­ and of the fact I am sure—­we might expect that the agent likewise would be one least apt to create suspicion.  There are no portieres, no opportunity for the use of another venom; and besides, that has lost its novelty, and so its value.  Similarly there is no use of food or wine in the scene, precluding something else along the toxin order.

“Our unknown realizes that the safest place to commit murder is where there is a crowd.  He has followed that principle consistently.  In the case of the heavy man, who has a bit of business before the camera where he drinks the contents of a little bottle, the very cleverest thing is to use belladonna, because Shirley has employed it for his eyes, and because”—­ maliciously, almost—­“it leads immediately to the hypothesis of suicide.”

“Ye gods, Craig!” A sudden thought struck me and rather terrified me.  “Do you suppose Enid Faye suggested the use of the drug to Shirley as part of the scheme to kill him?  Is she—­”

“I prefer,” Kennedy interrupted—­“I prefer to suppose that the guilty person overheard her, or perhaps saw him buy it or learned in some other way that he was going to use it.”

Completely taken up with this new line of thought, I failed to question Kennedy further, and it was just as well because most of the people were on their way down to the projection room, not only those we wished present, but practically everyone of sufficient importance about the studio to feel that he could intrude.

Kennedy turned to Mackay, who had taken no part in our discussion, although an interested listener.  “You have the bag and all the evidence?”

“Yes!” Mackay picked it up.  “Watkins, the camera man, watched it for me while Jameson and I went after that drug.”

Kennedy stooped down quickly, but it was locked and had not been tampered with.

In the corridor by the dressing rooms we met Kauf, and Kennedy stopped him.

“How long would it take to make a print from the scene where Shirley took the poison?”

“We could have it ready in half an hour, in a case of grim necessity.”

“Half an hour?” I exclaimed at that, in disbelief.  “You couldn’t begin to dry the negative in that time, Kauf.”

He glanced at me tolerantly.  “We make what is called a wet print; that is, we print from the negative while it is still wet and so we only have the positive to dry.  Then we put it on drums in a forced draught of hot air.  The result is not very good, but it’s a fine thing sometimes to get a picture of a parade or some accident in a theater right after it happens.”

“Will you do it for me, Kauf?” Kennedy broke in, impatiently.  “This is a case of grim necessity,” he added.

Kauf hurried off and we made our way across the yard to the stairs leading down into the basement and to the projection room specified by Kennedy.  Here Manton was waiting, uneasy, flushed, his face gathered in a frown and his hands clenching and unclenching in his nervousness.