“That won’t hurt you, Patsy, my lad,” said Nick.  “The weather’s good.  You’re to keep an eye on the whole household, but on Miss Stevens especially.

“This is the way the case looks at present:  The girl is doing the work on this end in connection with some confederate concealed in Colonel Richmond’s house.

“You understand the game.  It’s to work the spirit racket on Colonel Richmond until he buys the jewels from his daughter or her husband, and gives them to Miss Stevens.

“You must watch for the system by which she communicates with her confederate in Richmond’s house.  They work the mails, but there must be some quicker means to use in emergencies.

“Try to snare a letter, or get a sight of the other party.

“And be sure not to jump at conclusions, Patsy.  I’ve told you how the case looks, but it may be any other way.  I haven’t begun to work down to it yet.”

Nick mounted his horse, and Patsy strolled away in the direction of the Stevens house.

When the detective got back to Colonel Richmond’s, it was well along in the afternoon.

He spent the remainder of his day in exploring the secret recesses of the old house.  It was, indeed, a marvelous place, and Nick got a very high opinion of the ingenuity of the man who had designed its mysterious passages.

He got little else, however.  One or two discoveries he certainly made.  They were important as indicating that somebody had recently been in the secret passages.

There was nothing to show what that person had been doing there, but the probability was, of course, that he had concealed himself in the old part of the house while preparing for his operations in Mrs. Pond’s room, or while escaping from them.

These indications were very vague, and did not point to the principal in this affair—­that mysterious thief who worked invisibly and by such strange methods.

After dinner Horace Richmond took Nick aside, for what he termed a discussion of “this ghostly rot.”

“The very devil is in this business,” said Horace.  “The servants are getting scared out of their wits.

“They all sleep in the old part of the house, you know, and there isn’t one of them who hasn’t some story to tell of what goes on there in the night.

“Some of these yarns are the old-fashioned business about sighs and groans, and doors opening and shutting without anybody to open and shut them.

“But under it all I must say that there seems to be a basis of fact.  There’s John Gilder, the coachman.  You’ve seen him, Does he look like a man who can be scared easily?”

“I should say not,” laughed Nick.  “He looks to me like a Yankee horse-trader, who is too intimate with the devil and his ways to be at all alarmed about them.”

“Just so.  Well, John Gilder came to me to-day, and told me just as calmly as I’d tell you the time of day, that he’d seen the ghost of Miss Lavina Richmond.  He saw her right in this room where we are now.”