Bobby started.  The memory of that eerie grief was still uncomfortable in his brain.  Could there have been actually a woman at the stagnant lake that afternoon and close to the house to-night—­some mysterious friend who assumed grave risks in his service?  He recognized Robinson’s logic.  Unless there were something in that far-fetched theory, Katherine faced a situation nearly as serious as his own.  Robinson straightened.  At the same moment the scraping of a window reached them.  Bobby glanced at the newer wing.  Katherine leaned from her window.  The coincidence disturbed him.  In Robinson’s mind, he knew, her anxiety would assume a colour of guilt.  Her voice, moreover, was too uncertain, too full of misgivings: 

“What is going on down there?  There have been no—­no more tragedies?”

“Would you mind joining us for a moment?” Robinson asked.

She drew back.  The curtain fell over her lighted window.  The darkness of the court was disturbed again only by the limited radiance of the flashlight.  She came hurriedly from the front door.

“I saw you gathered here.  I heard you talking.  I wondered.”

“You knew there were footprints in this court,” Robinson said harshly, “that Howells connected them with the murderer of your uncle.”

“Yes,” she answered simply.

“Why then,” he asked, “did you attempt to obliterate them?”

She laughed.

“What do you mean?  I didn’t.  I haven’t been out of the house since just after luncheon.”

“Can you prove that?”

“It needs no proof.  I tell you so.”

The flashlight exposed the ugly confidence of Robinson’s smile.

“I am sorry to suggest the need of corroboration.”

“You doubt my word?” she flashed.

“A woman,” he answered, “has obliterated valuable testimony, I shall make it my business to punish her.”

She laughed again.  Without another word she turned and reentered the house.  Robinson’s oath was audible to the others.

“We can’t put up with that sort of thing, sir,” Rawlins said.

“I ought to place this entire household under arrest,” Robinson muttered.

“As a lawyer,” Graham said easily, “I should think with your lack of evidence it might be asking for trouble.  There is Paredes who acknowledges he was in the court.”

“All right.  I’ll see what he’s got to say.”

He started for the house.  Bobby lingered for a moment with Graham.

“Do you know anything about this, Hartley?”

“Nothing,” Graham whispered.

“Then you don’t think Katherine—­”

“If she’d done it she’d have taken good care not to be so curious.  I doubt if it was Katherine.”

They followed the others into the hall.  Bobby, scarcely appreciating why at first, realized there had been a change there.  Then he understood:  Robinson faced an empty chair.  The hall was pungent with cigarette smoke, but Paredes had gone.