“It has been very pleasant, sir, until the last month or so,” regretfully, yet evidently glad of the opportunity to talk, lingering with one hand on the knob of the door.  “Since then things haven’t been just the same.”

“In what way?”

“Well, I don’t exactly know, sir.  Miss Natalie seems to change her mind, an’ we never can please her.  That’s the trouble mostly.  Last night I waited up until you all went to bed, an’ then locked the house, the way she told me to.  But that didn’t suit her at all, for she stopped me on the stairs, an’ made me go back an’ leave the side door unlocked—­just said she’d attend to that herself.”

“Miss Natalie told you?  You are sure, Sexton?”

“Oh, it was her, sir; there was a light burning in the hall, an’ she was all dressed up as though she was goin’ out.  ’Taint the first time, either.  I ain’t got no right to say anything, but it puzzles me what she wants to go out for at that time o’ night.  And I thought maybe I ought to speak to Mr. Percival Coolidge about it.”

“No.  I wouldn’t, Sexton,” said West quietly.  “It would likely enough only get you into trouble.  Probably she cannot sleep well, and so walks in the garden.  Anyway this is none of our business, my man.  Where are Miss Natalie’s apartments?”

“In the other wing, sir; the first door beyond the head of the stairs.”

“And the door you were asked to leave open?”

“At the farther end of the hall.”

As West made no further effort to continue the conversation, but began to carelessly roll a cigarette, Sexton slipped silently through the opening, the valise in his hand, and closed the door behind him.  West touched a match to the cigarette, scarcely aware of the action.

This attempt to dig information out of a servant was not a pleasant experience, yet he felt that in this case it was fully justified.  To be sure he had gained little, yet that little helped to clear away the fog, and sustain the girl’s theory that she was being impersonated by another even to her own servants.  If West had retained any lingering doubt as to what had occurred the previous night, this doubt had entirely vanished in the face of Sexton’s testimony.  His visitor, and the one who had ordered the servant to leave the side door unlocked, had been the same—­not Natalie Coolidge, but strangely resembling her.  Whoever she was, she knew the house well, and possessed some means of entrance.  Whatever else her purpose might be, one object was clearly connected with the presence there of Percival.  She had sought his room, fleeing immediately on discovering it to be occupied by another.  Very well! this meant that he already had two distinct lines of investigation opened to him—­the woman, and the man.  The first was like pursuing a shadow, but Coolidge was real enough.  He determined to keep in touch with the fellow, confident that he would thus be eventually led to a discovery of his companion.  Beyond all question, they were involved in the same scheme of conspiracy.  West had deliberately arrived at this conclusion, rather pleased at his success, when a gentle knock sounded at the door.