When the nobleman and his secretary had left, my friend flung himself at once with characteristic eagerness into the investigation.

The boy’s chamber was carefully examined, and yielded nothing save the absolute conviction that it was only through the window that he could have escaped.  The German master’s room and effects gave no further clue.  In his case a trailer of ivy had given way under his weight, and we saw by the light of a lantern the mark on the lawn where his heels had come down.  That one dint in the short, green grass was the only material witness left of this inexplicable nocturnal flight.

Sherlock Holmes left the house alone, and only returned after eleven.  He had obtained a large ordnance map of the neighbourhood, and this he brought into my room, where he laid it out on the bed, and, having balanced the lamp in the middle of it, he began to smoke over it, and occasionally to point out objects of interest with the reeking amber of his pipe.

“This case grows upon me, Watson,” said he.  “There are decidedly some points of interest in connection with it.  In this early stage, I want you to realize those geographical features which may have a good deal to do with our investigation.

“Look at this map.  This dark square is the Priory School.  I’ll put a pin in it.  Now, this line is the main road.  You see that it runs east and west past the school, and you see also that there is no side road for a mile either way.  If these two folk passed away by road, it was this road.”

GRAPHIC

“Exactly.”

“By a singular and happy chance, we are able to some extent to check what passed along this road during the night in question.  At this point, where my pipe is now resting, a county constable was on duty from twelve to six.  It is, as you perceive, the first cross-road on the east side.  This man declares that he was not absent from his post for an instant, and he is positive that neither boy nor man could have gone that way unseen.  I have spoken with this policeman to-night and he appears to me to be a perfectly reliable person.  That blocks this end.  We have now to deal with the other.  There is an inn here, the Red Bull, the landlady of which was ill.  She had sent to Mackleton for a doctor, but he did not arrive until morning, being absent at another case.  The people at the inn were alert all night, awaiting his coming, and one or other of them seems to have continually had an eye upon the road.  They declare that no one passed.  If their evidence is good, then we are fortunate enough to be able to block the west, and also to be able to say that the fugitives did not use the road at all.”

“But the bicycle?” I objected.