As she ended, Billy darted in from the hall, his beady little black eyes gleaming with excitement, a long, wicked-looking butcher knife in his hand.

"Key, kitchen door, please!" he said, addressing his mistress.

"Key?" said Miss Cornelia, startled. "What for?"

For once Billy's polite little grin was absent from his countenance.

"Somebody outside trying to get in," he chattered. "I see knob turn, so," he illustrated with the butcher knife, "and so--three times."

The detective's hand went at once to his revolver.

"You're sure of that, are you?" he said roughly to Billy.

"Sure, I sure!"

"Where's that hysterical woman Lizzie?" queried Anderson. "She may get a bullet in her if she's not careful."

"She see too. She shut in closet--say prayers, maybe," said Billy, without a smile.

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The picture was a ludicrous one but not one of the little group laughed.

"Doctor, have you a revolver?" Anderson seemed to be going over the possible means of defense against this new peril.

"No."

"How about you, Beresford?"

Beresford hesitated.

"Yes," he admitted finally. "Always carry one at night in the country." The statement seemed reasonable enough but Miss Cornelia gave him a sharp glance of mistrust, nevertheless.

The detective seemed to have more confidence in the young idler.

"Beresford, will you go with this Jap to the kitchen?" as Billy, grimly clutching his butcher knife, retraced his steps toward the hall. "If anyone's working at the knob--shoot through the door. I'm going round to take a look outside."

Beresford started to obey. Then he paused.

"I advise you not to turn the doorknob yourself, then," he said flippantly.

The detective nodded. "Much obliged," he said, with a grin. He ran lightly into the alcove and tiptoed out of the terrace door, closing the door behind him. Beresford and Billy departed to take up their posts in the kitchen. "I'll go with you, if you don't mind--" and Jack Bailey had followed them, leaving Miss Cornelia and Dale alone with the Doctor. Miss Cornelia, glad of the opportunity to get the Doctor's theories on the mystery without Anderson's interference, started to question him at once.

"Doctor."

"Yes." The Doctor turned, politely.

"Have you any theory about this occurrence to-night?" She watched him eagerly as she asked the question.

He made a gesture of bafflement.

"None whatever--it's beyond me," he confessed.

"And yet you warned me to leave this house," said Miss Cornelia cannily. "You didn't have any reason to believe that the situation was even as serious as it has proved to be?"

"I did the perfectly obvious thing when I warned you," said the Doctor easily. "Those letters made a distinct threat."