On the train Kennedy left me, to look through the other cars, having the idea that Phelps might be aboard also. But there were no signs of the banker. We would reach Tarrytown first unless he had chosen to motor out.

Mackay was waiting at the station to meet us and to take us to the house. The little district attorney was obviously excited.

"Was the place guarded well last night?" asked Kennedy, almost before we had shaken hands.

"Yes—that is, I thought it was. That's what I want to tell you. After you left with Manton and Werner the rest of the company packed up and pulled out in the two studio cars. I was a little in doubt what to do about Phelps, but he settled it himself by announcing that he was going to town. The coroner came and issued the permit to remove the body and that was taken away. I think the house and the presence of the dead girl and all the rest of it got on Phelps's nerves, because he was irritable and impatient, unwilling to wait for his own car, until finally I drove him to the station myself."

"Was anyone, any of those on our list of possible suspects at least, alone in the room—or in the house?"

"Not while I was there," Mackay replied. "I took good care of that. Then, when everyone was gone and while Phelps was waiting for me, I detailed two of my deputies to stay on guard—one inside and one outside—for the night. I thought it sufficient precaution, since you had made your preliminary examination."

"And—" Kennedy nodded, seeking to hurry the explanation.

"And yet," added Mackay, "some one entered the house last night in spite of us."

Kennedy fairly swore under his breath. He seemed to blame himself for some omission in his investigation the previous afternoon.

"How did it happen?" I asked, rather excitedly.

"It was about three o'clock, the guards tell me. The man inside was dozing in a chair before the living-room fireplace. He was placed so he could command a view of the doorway to the library as well as the stairs and reception hall. All at once he was awakened by a shot and a cry from outside. He jumped up and ran toward the library. As he did so the portieres bellied in toward him, as if in stiff sudden draught, or as if some one had darted into their folds quickly, then out. With no hesitation he drew his own weapon, rushing the curtains. There was no one secreted about them. Then, with the revolver in one hand, he switched on the lights. The room was empty. But one pair of French windows at the farther end were wide open and it was that which had caused the current of air. He ran over and found the lock had been forced. It was not even an artistic job of jimmying."

"What about the deputy posted outside?" prompted Kennedy.

"That's the strange part of it. He was alert enough, but it's a big house to watch. He swears that the first thing he knew of any trouble was the sharp metallic click which he realized later was the sound made by the intruder in forcing the catch of the French window. It was pretty loud out in the quiet of a Tarrytown night.

"He started around from the rear and then the next thing he caught was the outline of a shadowy slinking figure as a man dropped out of the library. He called. The intruder broke into a run, darting across the open space of lawn and crashing through the shrubbery without any further effort at concealment. My man called again and began to chase the stranger, finally firing and missing. In the shrubbery a sharp branch whipped him under the chin just as he obtained a clear view of the outlined figure of his quarry and as he raised his weapon to shoot again. The revolver was knocked from his hand and he was thrown back, falling to the ground and momentarily stunned. Whoever broke into the library got away, of course."

"What did the intruder look like?" There was an eagerness in Kennedy's manner. I grasped that the case was beginning to clarify itself in his mind.

Mackay shook his head. "There was no moon, you know, and everything happened swiftly.

"But was he tall or short or slender or stout—the deputy must have got some vague idea of him at least."

"It was one of my amateur deputies," Mackay admitted, reluctantly. "He thought the man was hatless, but couldn't even be sure of that."

"Were there footprints, or fingerprints—"

"No, Mr. Kennedy, we're out of luck again. When he jumped out he fell to his hands and knees in a garden bed. The foot marks were ruined because his feet slid and simply made two irregular gashes. The marks of his hands indicated to me, anyhow, that he wore heavy gloves, rubber probably."

"Any disturbance in the library?"

"Not that I could notice. That's why I phoned you at once. I'm hoping you'll discover something."

"Well—" Kennedy sighed. "It was a wonderful opportunity to get to the bottom of this."

"I haven't told you all yet, Mr. Kennedy," Mackay went on. "There was a second man, and—"

"A second man?" Kennedy straightened, distinctly surprised. "I would swear this whole thing was a one-man job."

"They weren't together," the district attorney explained. "That's why I didn't mention them both at once. But my deputy says that when he was thrown by the lash of the branch he was unable to move for a few seconds, on account of the nerve shock I suppose, and that while he was motionless, squatted in a sort of sitting position with hands braced behind him, just as he fell, he was aware of a second stranger concealed in the shrubbery.

"The second fellow was watching the first, without the question of a doubt. While the deputy slowly rose to his feet this other chap started to follow the man who had broken into the house. But at that moment there was the sudden sound of a self-starter in a car, then the purr of a motor and the clatter of gears. Number one spun off in the darkness of the road as pretty as you please. Number two grunted, in plain disgust.

"By this time my deputy had his wind. His revolver was gone, but he jumped the second stranger with little enough hesitation and they battled royally for several minutes in the dark. Unfortunately, it was an unequal match. The intruder apparently was a stocky man, built with the strength of a battleship. He got away also, without leaving anything behind him to serve for identification."

"You have no more description than of the first man?"

"Unfortunately not. Medium height, a little inclined to be stocky, strong as a longshoreman—that's all."

"Are you sure your deputy isn't romancing?"

"Positively! He's the son of one of our best families here, a sportsman and an athlete. I knew he loved a lark, or a chance for adventure, and so I impressed him and a companion as deputies when I met them on the street on my way up to Phelps's house just after the tragedy."

Kennedy lapsed into thought. Who could the self-constituted watcher have been? Who was interested in this case other than the proper authorities? Apparently some one knew more than Mackay, more than Kennedy. Whoever it was had made no effort to communicate with any of us. This was a new angle to the mystery, a mystery which became deeper as we progressed.

At the house Kennedy first made a careful tour of the exterior, but found nothing. Mackay had doubled his guards and had sent Phelps's servants away so that there could be no interference.

Once inside, I noticed that Kennedy seemed indisposed to make another minute search of the library. He went over the frame of the French window with his lens carefully, for fingerprints. Finding nothing, he went back directly to the portieres.

For several moments he stood regarding them in thought. Then he began a most painstaking inspection of the cloth with the pocket glass, beginning at the library side.

I remembered that first scene in the manuscript which Kennedy had insisted I read. I recalled the suspicion which had flashed to me before the message from Mackay had disturbed both Kennedy's thoughts and mine. Stella Lamar had thrust her bare arm through this curtain. A needle, cleverly concealed in the folds, might easily have inflicted the fatal scratch. It was for a trace of the poison point that Kennedy searched. Of that I was sure, knowing his methods.

I glanced up and down the heavy hanging silk, looking for the glint of fine sharp steel as Kennedy had done before starting his inspection with the glass. The color of the silk, a beautiful heavy velour, was a strange dark tint very close to the grained black-brown of the woodwork. Both the thickness of the material and its dull shade made the portieres serve ideally for the purpose assumed now both by Kennedy and myself. A tiny needle might remain secreted within their folds for days. Nothing, certainly, caught my naked eye.

At last a little exclamation from Kennedy showed us that he had discovered something. I moved closer, as did Mackay.

"It's lucky none of us toyed with these curtains yesterday," he remarked, with a slight smile of gratification. "There might have been more than one lying where Stella Lamar lies at the present moment."

With wholesome respect neither Mackay nor myself touched the silk as Kennedy pointed. There were two small holes, almost microscopic, in the close-woven material. About the one there was the slightest discoloration. Not a fraction of an inch away I saw two infinitesimal spots of a dark brownish-red tinge.

"What does it mean?" I asked, although I could guess.

"The dark spots are blood, the discoloration the poison from the needle."

"And the needle?"

He shrugged his shoulders. "That's where our very scientific culprit has forestalled me, Walter! The needle was in these curtains all day yesterday. Unfortunately, I did not study the manuscript, did not attach any importance to Miss Lamar's scene at the portieres."

"The man who broke in last night—"

"Removed the needle, but"—almost amused—"not the traces of it. You see, Walter, after all, the scientific detective cannot be forestalled even by the most scientific criminal. There is nothing in the world which does not leave its unmistakable mark behind, provided you can read it. The hole in the cloth serves me quite as well as the needle itself."

Very suddenly a voice from behind us interrupted.

"Find something?"

I turned, startled, to see Emery Phelps. There was a distinct eagerness in the banker's expression.

"Yes!" Kennedy faced him, undisturbed, apparently not surprised. His scrutiny of Phelps's face was frank and searching. "Yes," he repeated, "bit by bit the guilty man is revealing himself to us."