“What do you mean?”

“He was not there when he did it,” explained Fisher.  “It’s a poor sort of murderer who can’t murder people when he isn’t there.”

“You seem to be talking merely for the sake of mystification,” said Brain.  “If you have any practical advice to give you might as well make it intelligible.”

“The only practical advice I can suggest,” said Fisher, thoughtfully, “is a little research into local topography and nomenclature.  They say there used to be a Mr. Prior, who had a farm in this neighborhood.  I think some details about the domestic life of the late Mr. Prior would throw a light on this terrible business.”

“And you have nothing more immediate than your topography to offer,” said Brain, with a sneer, “to help me avenge my friend?”

“Well,” said Fisher, “I should find out the truth about the Hole in the Wall.”

* * *

That night, at the close of a stormy twilight and under a strong west wind that followed the breaking of the frost, Leonard Crane was wending his way in a wild rotatory walk round and round the high, continuous wall that inclosed the little wood.  He was driven by a desperate idea of solving for himself the riddle that had clouded his reputation and already even threatened his liberty.  The police authorities, now in charge of the inquiry, had not arrested him, but he knew well enough that if he tried to move far afield he would be instantly arrested.  Horne Fisher’s fragmentary hints, though he had refused to expand them as yet, had stirred the artistic temperament of the architect to a sort of wild analysis, and he was resolved to read the hieroglyph upside down and every way until it made sense.  If it was something connected with a hole in the wall he would find the hole in the wall; but, as a matter of fact, he was unable to find the faintest crack in the wall.  His professional knowledge told him that the masonry was all of one workmanship and one date, and, except for the regular entrance, which threw no light on the mystery, he found nothing suggesting any sort of hiding place or means of escape.  Walking a narrow path between the winding wall and the wild eastward bend and sweep of the gray and feathery trees, seeing shifting gleams of a lost sunset winking almost like lightning as the clouds of tempest scudded across the sky and mingling with the first faint blue light from a slowly strengthened moon behind him, he began to feel his head going round as his heels were going round and round the blind recurrent barrier.  He had thoughts on the border of thought; fancies about a fourth dimension which was itself a hole to hide anything, of seeing everything from a new angle out of a new window in the senses; or of some mystical light and transparency, like the new rays of chemistry, in which he could see Bulmer’s body, horrible and glaring, floating in a lurid halo over the woods and the wall.  He was haunted also with the hint, which somehow seemed to be equally horrifying, that it all had something to do with Mr. Prior.  There seemed even to be something creepy in the fact that he was always respectfully referred to as Mr. Prior, and that it was in the domestic life of the dead farmer that he had been bidden to seek the seed of these dreadful things.  As a matter of fact, he had found that no local inquiries had revealed anything at all about the Prior family.