“Did you ever try knitting when you wanted to think?” she queried sweetly, after a pause in which the detective tramped from one side of the room to the other, brows knotted, eyes bent on the floor.

“No,” grunted the detective.  He took out a cigar—­bit off the end with a savage snap of teeth—­lit it—­resumed his pacing.

“You should, sometimes,” continued Miss Cornelia, watching his troubled movements with a faint light of mockery in her eyes.  “I find it very helpful.”

“I don’t need knitting to think straight,” rasped Anderson indignantly.  Miss Cornelia’s eyes danced.

“I wonder!” she said with caustic affability.  “You seem to have so much evidence left over.”

The detective paused and glared at her helplessly.

“Did you ever hear of the man who took a clock apart—­and when he put it together again, he had enough left over to make another clock?” she twitted.

The detective, ignoring the taunt, crossed quickly to Dale.

“What do you mean by saying that paper isn’t where you put it?” he demanded in tones of extreme severity.  Miss Cornelia replied for her niece.

“She hasn’t said that.”

The detective made an impatient movement of his hand and walked away—­as if to get out of the reach of the indefatigable spinster’s tongue.  But Miss Cornelia had not finished with him yet, by any means.

“Do you believe in circumstantial evidence?” she asked him with seeming ingenuousness.

“It’s my business,” said the detective stolidly.  Miss Cornelia smiled.

“While you have been investigating,” she announced, “I, too, have not been idle.”

The detective gave a barking laugh.  She let it pass.  “To me,” she continued, “it is perfectly obvious that one intelligence has been at work behind many of the things that have occurred in this house.”

Now Anderson observed her with a new respect.

“Who?” he grunted tersely.

Her eyes flashed.

“I’ll ask you that!  Some one person who, knowing Courtleigh Fleming well, probably knows of the existence of a Hidden Room in this house and who, finding us in occupation of the house, has tried to get rid of me in two ways.  First, by frightening me with anonymous threats —­and, second, by urging me to leave.  Someone, who very possibly entered this house tonight shortly before the murder and slipped up that staircase!”

The detective had listened to her outburst with unusual thoughtfulness.  A certain wonder—­perhaps at her shrewdness, perhaps at an unexpected confirmation of certain ideas of his own —­grew upon his face.  Now he jerked out two words.

“The Doctor?”

Miss Cornelia knitted on as if every movement of her needles added one more link to the strong chain of probabilities she was piecing together.

“When Doctor Wells said he was leaving here earlier in the evening for the Johnsons’ he did not go there,” she observed.  “He was not expected to go there.  I found that out when I telephoned.”