“Quite so.  We will come to the bicycle presently.  To continue our reasoning:  if these people did not go by the road, they must have traversed the country to the north of the house or to the south of the house.  That is certain.  Let us weigh the one against the other.  On the south of the house is, as you perceive, a large district of arable land, cut up into small fields, with stone walls between them.  There, I admit that a bicycle is impossible.  We can dismiss the idea.  We turn to the country on the north.  Here there lies a grove of trees, marked as the ‘Ragged Shaw,’ and on the farther side stretches a great rolling moor, Lower Gill Moor, extending for ten miles and sloping gradually upward.  Here, at one side of this wilderness, is Holdernesse Hall, ten miles by road, but only six across the moor.  It is a peculiarly desolate plain.  A few moor farmers have small holdings, where they rear sheep and cattle.  Except these, the plover and the curlew are the only inhabitants until you come to the Chesterfield high road.  There is a church there, you see, a few cottages, and an inn.  Beyond that the hills become precipitous.  Surely it is here to the north that our quest must lie.”

“But the bicycle?” I persisted.

“Well, well!” said Holmes, impatiently.  “A good cyclist does not need a high road.  The moor is intersected with paths, and the moon was at the full.  Halloa! what is this?”

There was an agitated knock at the door, and an instant afterwards Dr. Huxtable was in the room.  In his hand he held a blue cricket-cap with a white chevron on the peak.

“At last we have a clue!” he cried.  “Thank heaven! at last we are on the dear boy’s track!  It is his cap.”

“Where was it found?”

“In the van of the gipsies who camped on the moor.  They left on Tuesday.  To-day the police traced them down and examined their caravan.  This was found.”

“How do they account for it?”

“They shuffled and lied—­said that they found it on the moor on Tuesday morning.  They know where he is, the rascals!  Thank goodness, they are all safe under lock and key.  Either the fear of the law or the Duke’s purse will certainly get out of them all that they know.”

“So far, so good,” said Holmes, when the doctor had at last left the room.  “It at least bears out the theory that it is on the side of the Lower Gill Moor that we must hope for results.  The police have really done nothing locally, save the arrest of these gipsies.  Look here, Watson!  There is a watercourse across the moor.  You see it marked here in the map.  In some parts it widens into a morass.  This is particularly so in the region between Holdernesse Hall and the school.  It is vain to look elsewhere for tracks in this dry weather, but at that point there is certainly a chance of some record being left.  I will call you early to-morrow morning, and you and I will try if we can throw some little light upon the mystery.”