room, furnished as half-lounging room, half office. There was a large flat-top mahogany desk in the centre, with a sofa and several upholstered chairs, evidently for use as well as ornament. On the walls were pictures of value, views of foreign places, and oil paintings that a mere novice could see were works of art. There was that in the room which suggested education and refinement.

A telephone was on the desk, and loose papers partly written upon bore evidence that the detective had been busy at work when I arrived.

At a motion from my host I seated myself in one of the large arm chairs facing him, while he remained standing.

I saw that he was a man about thirty-eight or forty years old, straight as an arrow and splendidly proportioned. He was dressed in a well-fitting gray suit.

The light was from above, and Oakes's face showed well—the clear-cut nose and generous mouth of the energetic American.

He looked at me critically with deep-set, steady blue eyes, then smiled slightly in a well-controlled, dignified manner.

"Mr. Stone, I am very glad that you were able to come tonight. Make yourself at home," he said.

I made an appropriate answer of some kind, and then Oakes took the seat near me and began, without further ceremony:

"I have arranged that our friend Dr. Moore shall come here this evening; meanwhile, I will inform you briefly of the subject in hand."

"A few months ago Mandel & Sturgeon the attorneys, whom you doubtless know, consulted me regarding the unpleasant happenings at the mansion of one Odell Mark, up-State, in the town of Mona.

"Now, Mandel & Sturgeon suggested, also, that you might care to help unravel the matter, acting as their legal representative.

"I have completed my arrangements for starting on the case, and am particularly glad to find that you are a friend of Dr. Moore and that you had expressed to him a desire to enter into some such affair. I assure you, however, that Mandel & Sturgeon had previously spoken of you and that this offer was coming as a business proposition. The fact that you and Dr. Moore had spoken of such a trip is merely a coincidence."

He spoke with a well-modulated voice, and a fluency that told of the intelligence of the man. His eyes fixed me, but not in an embarrassing manner; it was the habit of observation that prompted their concentration—that was obvious.

His forehead was high and slightly furrowed with two vertical wrinkles between the eyebrows. His face was mobile and expressive at times, then suddenly calm. In my very brief observation I knew that he was able to govern its expression well.

In the days that were coming, I learned that in the presence of danger or possible trickery that face became stony and immovable, a mask that talked and commanded, while hiding the suppressed energy of the man.

The bell rang before Oakes could proceed with his statement, and Dr. Moore was shown in. His coming enlivened us both, and after a few words of greeting I found the opportunity, and said:

"Mr. Oakes, it is not exactly clear to me why Mandel & Sturgeon recommended me as their representative. They have so many men in their office whom they might use in that capacity."

"Doubtless you will hear from them yourself before we go, Mr. Stone. Meantime, I may explain. You were in their employ at one time, I believe?"

"Yes, a great many years ago."

"They think that some legal matters might arise, where a man on the spot would be of value, and it seems best that their representative with me should be one not easily identified as working with them. You know, Mr. Stone, we are not advertising our mission."

"I have been in Mona as Mr. Clark, their agent, looking after the Mansion and other property, and if I return there, it must be under some business pretext, or people will suspect me. You, being an independent party, not known as connected with the firm in any way, can accompany me in the rôle of a friend on an outing, or as a possible purchaser. You see, we are trying to solve a mystery, so the less attention we attract the better."

"I see. So you have been there already, Mr. Oakes?"

"Yes, gentlemen. I will tell you about this affair very briefly now. You will learn more later, if you enter upon its solution with me.

"The Mansion was originally the property of George Mark, who died some years ago, leaving it to his two sons, Winthrop and Odell. Both were single men at that time, but Odell married a couple of years ago and persuaded his brother to sell his share of the property to him. Winthrop, who was the older, did not care to part with it, but finally disposed of his interest to his brother, who immediately moved into the place with his bride. The old servants were still in charge, and everything had been kept up to a high standard of excellence, although no one had lived there since the old man died.

"Odell had travelled some, and lived mostly in the city, while Winthrop had been engrossed in amassing a large fortune in speculation. He had resided in Mona, keeping his own place, saying he did not care for the Mansion as a home after his father died."

"Then why did he not care to give up his interest to his brother?" asked Moore.

"That is as yet a mystery. But, as he was a great business man, it is supposed by some that he saw opportunities to convert the vast grounds into town lots, and sell at a great advance some day when Mona should boom, as the town will sooner or later, owing to its natural advantages. He told many, however, that it was merely a sentiment with him, the place having belonged in Colonial times to the family. Be that as it may, however, he finally sold, and never would buy it back again, even after the mystery had made it practically valueless.

"His brother offered to sell it back for next to nothing, but Winthrop only laughed, and refused. This conduct seemed to dispose of the supposition that he was in any way responsible for the occurrences there which had such a depressing effect in the value of the property."

"Then, if mixed up, he had a deeper motive," said I.

"Yes—if he has really been involved in the mystery at all. You must remember, however," said Oakes, "that his story may be true. Having disposed of his share of the property, he may have seen no reason for bothering with it again, at least until it was clear of the depressing occurrences which had lowered its value from half a million to practically nothing."

"Goodness! What were these mysteries?" said Moore, with a feigned shudder. "Evidently, they are unpopular."

Oakes proceeded slowly.

"They consist of a series of assaults on those who have occupied the house, and they are conducted in such a way that detection has been impossible.

"One evening Mrs. Mark was heard to shriek in her bedroom, and when found by her husband was insane from fright. In her ravings she spoke of a terrible thing choking her, and of a swishing sound. She never regained her reason, and is now in an insane asylum. Alienists at first thought that she had an experience common to those going mad—that she had been subject to a delusion. But evidences were against this, as she had in no way shown any signs of mental trouble before. While she was being cared for at the Mansion, the two nurses in charge had similar experiences. They reported hearing a tread on the stairs one night and of seeing a figure disappear into the dining-room. One stated up and down that it was a woman.

"The patient was removed from the place. Then Mr. Odell Mark received such a scare