A little smile played across the face of the other.

"I haven't the slightest objection," he said. "Where will you start?"

"In the bas.e.m.e.nt," said T. B.; "that is to say, in your kitchen."

The millionaire led the way down the stairs, and descended the back stairway which led to the domain of the absent cook. He turned on the electric light as they entered.

There was no sign of an intruder.

"That is the cellar door," indicated Mr. Farrington, "this the larder, and this leads to the area pa.s.sage. It is locked."

T. B. tried the handle, and the door opened readily.

"This at any rate is open," he said, and entered the dark pa.s.sageway.

"A mistake on the part of the butler," said the puzzled Mr. Farrington.

"I have given the strictest orders that all these doors should be fastened. You will find the area door bolted and chained."

T. B. threw the rays of his electric torch over the door.

"It doesn't seem to be," he remarked; "in fact, the door is ajar."

Farrington gasped.

"Ajar?" he repeated. T. B. stepped out into the well of the tiny courtyard. It was approached from the street by a flight of stone stairs.

T. B. threw the circle of his lamp over the flagged yard. He saw something glittering and stooped to pick it up. The object was a tiny gold-capped bottle such as forms part of the paraphernalia in a woman's handbag.

He lifted it to his nose and sniffed it.

"That is it," he said.

"What?" asked Mr. Farrington, suspiciously.

"The scent I detected in your hall," replied T. B. "A peculiar scent, is it not?" He raised the bottle to his nose again. "Not your ward's by any chance?"

Farrington shook his head vigorously.

"Doris has never been in this area in her life," he said; "besides, she dislikes perfumes."

T. B. slipped the bottle in his pocket.

Further examination discovered no further clue as to the third person, and T. B. followed his host back to the study.

"What do you make of it?" asked Mr. Farrington.

T. B. did not answer immediately. He walked to the window and looked out. The little crowd which had been attracted by the shots and arrival of the police ambulance had melted away. The mist which had threatened all the evening had rolled into the square and the street lamps showed yellow through the dingy haze.

"I think," he said, "that I have at last got on the track of Montague Fallock."

Mr. Farrington looked at him with open mouth.

"You don't mean that?" he asked incredulously.

T. B. inclined his head.

"The open door below--the visitor?" jerked the stout man, "you don't think Montague Fallock was in the house to-night?"

T. B. nodded again, and there was a moment's silence.

"He has been blackmailing me," said Mr. Farrington, thoughtfully, "but I don't think----"

The detective turned up his coat collar preparatory to leaving.

"I have a rather unpleasant job," he said. "I shall have to search those unfortunate men."

Mr. Farrington shivered. "Beastly," he said, huskily.

T. B. glanced round the beautiful apartment with its silver fittings, its soft lights and costly panellings. A rich, warm fire burnt in an oxidized steel grate. The floor was a patchwork of Persian rugs, and a few pictures which adorned the walls must have been worth a fortune.

On the desk there was a big photograph in a plain silver frame--the photograph of a handsome woman in the prime of life.

"Pardon me," said T. B., and crossed to the picture, "this is----"

"Lady Constance Dex," said the other, shortly--"a great friend of mine and my ward's."

"Is she in town?"

Mr. Farrington shook his head.

"She is at Great Bradley," he said; "her brother is the rector there."

"Great Bradley?"

T. B.'s frown showed an effort to recollect something.

"Isn't that the locality which contains the Secret House?"

"I've heard something about the place," said Mr. Farrington with a little smile.

"C. D.," said the detective, making for the door.

"What?"

"Lady Constance Dex's initials, I mean," said T. B.

"Yes--why?"

"Those are the initials on the gold scent bottle, that is all," said the detective. "Good night."