“You’re assuming that he had a key.”
“Of course he had a key. The guest across the ball saw him trying it on the other doors and heard it clink against the lock.”
“If he had a key to this room why did he try it on several other doors first?” propounded Average Jones. “As for the clinking noise, in which I’m a good deal interested—may I look at your key, Mrs. Hale?”
She handed it to him. He tried it on the lock, outside, jabbing at the metal setting. The resultant sound was dull and wooden. “Not much of the clink which our friend describes as having heard, is it?” he remarked.
“Then how could he get into my room?” cried Mrs. Hale.
“Are you sure your door was locked?”
“Certain. As soon as I missed the necklace I looked at the catch.”
“That was in the morning. But the night before?”
“I always slip the spring. And I know I did this time because it had been left unsprung so that Mr. Kirby’s mother could come in and out of my sitting-room, and I remember springing it when she left for bed.”
“Sometimes these locks don’t work.” Slipping the catch back, Average Jones pressed the lever down. There was a click, but the ward failed to slip. At the second attempt the lock worked. But repeated trials proved that more than half the time the door did not lock.