"He would be careful not to leave it lying about after the murder," I said. "It wasn't a man, I fancy, but a woman. Had it been a man, the glasses on the tray yonder would probably have been used. Besides, if criminals were always as careful as you suggest, there are few detectives who would be able to hunt them down. The very essence of your profession is looking for mistakes." Quarles turned to examine the French window. "The window was found closed," I said, "but there is little significance in that. If pulled to from the outside it fastens itself. "And cannot be opened from the outside, I observe," said Quarles. "How about the garden door, yonder?" The house was a corner one. There was a small square of garden, and in the high wall was a door, an exit into a side road. "It was locked," I answered. "So, unless the retreating person had a key, he would have to climb the wall," the professor remarked. "That would require some agility." "The person who committed so savage a murder would be likely to have sufficient strength for that," I said. "Quite so," Quarles returned thoughtfully, crossing to a leather-covered sofa and looking at it carefully. "Shall we interview the servants?" he said, after a pause. The man who had found his master that morning was calmer now, and told us a coherent story. Mr. Seligmann had arrived home just before midnight on Saturday. They had expected him earlier in the evening. As he entered the study, he said he was returning to Maidenhead as soon as he had looked through his letters. He had a cottage on the river, where he and Mrs. Seligmann had been for the past two or three weeks, and the master had paid these flying visits to Hampstead more than once. The man had gone to bed after taking in the tray with the glasses. It was his custom to put two or three glasses on the tray. There was no one with Mr. Seligmann. The study had not been opened on Sunday. When he entered it this morning his master was dead in the chair, and the man had immediately sent for the police. He had also telegraphed to Mrs. Seligmann. "Was it usual not to open the room when Mr. Seligmann was away?" I asked. "On Sundays, yes. Other days it would be opened." "It wasn't necessary for you to sit up until your master had gone?" "No. He constantly left his motor in the side road and went out through the garden. He had a key of the door." "Was the electric light on in the hall on Sunday morning?" "No; but I didn't switch it off on Saturday. I left it because two of the servants were finishing some work in the kitchen--hat trimming. They were having the Sunday off. They ought to be back directly." "You supposed the motor was waiting in the side road ready to take your master to Maidenhead," said Quarles. "Would it be in charge of a chauffeur?" "Yes, sir." "When your master left by the garden was it not thought advisable to see that the study window was securely fastened? I see there are shutters."