Claire gave the desired assurance, and rose from the table. She would have Jack's coffee saved for him in the drawing-room, she said. Anstruther lit a cigarette, and began to talk of crime. Crime and criminals had a fine fascination for him. Scotland Yard offered valuable inspiration for his new book on the criminal instinct, and in return he had been in a position to give the officials yonder one or two useful hints. The case he had on hand just now was a most fascinating one, but, of course, his lips were sealed for the present. Jack forgot his dislike in the fascination of the present.

"Stay here and finish your cigar," Anstruther said as he rose and pitched his cigarette into the fire. "I'll go into my study and work this thing out with the aid of my violin. I may be an hour or so, or I may be longer. If I have finished before eleven o'clock I'll come up with my fiddle, and we'll get Claire to play. If you require any more claret you can ring the bell."

Jack sat there for a time smoking and thinking matters over. Presently, from the study beyond, came the sound of music. Really, Anstruther was a wonderful man--he seemed able to do anything. He was not perhaps a great performer on the violin--his playing was a little too mechanical, and seemed to lack soul--but the execution was brilliant enough. Jack opened his cigarette case only to find that it was empty. There was a fresh supply in the pocket of his overcoat, which was hanging in the hall. He would be just in time for one more, and then he would join Claire in the drawing-room. The hall light had been turned low, so that, as Jack stood in the vestibule fumbling in his coat pocket, he was not visible, though he could see what was going on in the hall behind him.

There was a spot of light at the head of the staircase. Somebody was standing there looking down into the hall--somebody in a rough jacket buttoned to the throat and wearing a pair of rubber-soled shoes, for the intruder made not the slightest noise. Jack wondered if some impudent burglar was raiding the house at this hour. If so, he would get a warm reception presently. Jack stood there as the figure came down the stairs and turned along a corridor to the left of the drawing-room. But there was no challenge and no fight, for the simple reason that in the hall light, as the stranger passed, Jack recognized the face of Spencer Anstruther. There was no doubt about it; there was no possibility of a mistake here.

Inside the study the music once more began. Very gently Jack tried the handle of the door, but it was locked. Under ordinary circumstances this would have excited no suspicion; perhaps there was another way into the room by way of the corridor. But if so that did not explain why Anstruther was creeping about his own house in the semblance of a burglar, and wearing rubber-soled shoes. There was something creepy about the whole business. Jack returned to the vestibule again, and from there he passed into the garden. The study was at the side of the house, and a belt of shrubs outside afforded a pretty good cover. There was the study under with the blinds down and a strong light inside. Jack noted that it was a French window, a window frequently used, because the stone step outside had been worn by the pressing of many feet.

The smooth melody of Chopin was playing on inside. Jack stooped down to where he could see the lace flowers on the blind, and looked into the room. There was a little slit in the blind where the sun had worn it, and by this slit the whole of the room could be seen. The music had softened down to a piano passage taken very slowly. But Jack was not thinking of the music now at all, though the strains were soothing and flowing enough.

He rubbed his eyes to make sure that they did not deceive him. No, the room was plain enough, so was the sound of the music. And with it all the room was absolutely empty!