Kennedy turned the bit of glass over and over in his hand, examining it carefully.  I felt rather fearful, wondering if it might not contain some trace of the deadly poison which had so quickly killed Stella Lamar.  I even half expected to see Kennedy find some infinitesimal jagged edge or point which could have inflicted the fatal scratch.  Then I realized that McGroarty had handled the thing with impunity, perhaps had carried it about half a day.

Kennedy took his scarf pin.  On the outside of the little tube there was no trace of a label or marking of any sort.  All about, on the inside, however, the glass was spotted with dried light-yellow incrustations, resembling crystals and at first apt to escape even the sharpest scrutiny.  With the pin Kennedy scaled off one of these and put it under his pocket lens.  But he came to no conclusion.  Rather puzzled and nettled, he dropped the tiny bit of substance back into the tube, then replaced his pin in his scarf, and stowed this latest bit of possible evidence in his pocket carefully.

“How do you suppose it got in the car?” he asked.

“Some one must have dropped it and it must have rolled in that space by the edge of the mat,” replied the chauffeur.  “There was just room for it, too!  I never would have noticed it without taking up the mat.”

“It couldn’t be broken, by being trampled on?”

“Nope!  Not a chance!”

“How long could it have been there?”

“Two or three or four days—­since I cleaned up last.”

I remembered the cleverness shown by the guilty person in placing the needle in the curtain.  It seemed unlikely that this could be an accident.  “Isn’t it possible,” I suggested, “that this is a plant; that the tube was put there deliberately, to throw us off the track?”

“It’s quite likely,” he admitted.  “On the other hand, Walter, the very smartest criminal will do some foolish little thing, enough to ruin the most careful plans and preparations.”  He turned to McGroarty.  “Who rode in your car yesterday?”

“Mine’s the principals’ car,” boasted McGroarty.  “Going out I had Miss Lamar, Miss Loring, Mr. Gordon, Mr. Shirley, and Mr. Werner.  Coming back Mr. Werner was with you, and Miss Lamar—­well, there was only Miss Loring and Mr. Gordon and Mr. Shirley.”

“Did you notice how they acted?”

“They never says a word to each other on all the trip back, but I didn’t think it strange after what happened, although usually they’re always joking and laughing.”

“You brought the three to the studio here?”

“Yes.  They had to get out of make-up.”

“Did you leave the car then?”

“No, I hit it right for the garage.”

“Were you away from the car at Tarrytown?”

“Sure!  That was a long wait.  Peters, Manton’s chauffeur, and I found a couple of horseshoes and we were throwing them most of the time.”

“How long was the machine alone here in the yard this morning?”