“Why didn’t you say it was you, sir?” exclaimed that crestfallen individual, as the flashing light made manifest his mistake.  “When I heard you first, and see you come up out of that back passage, I made sure it was him; and if you’d a struggled, I’d have bashed your head as sure as eggs.”

“Thank you for nothing,” he responded testily.  “You might have remembered, however, that the man’s first got to get into the place before he can come downstairs.  Mr. Narkom,” turning to the superintendent, “I was just getting into bed when I thought of something I’d neglected to tell you; and as my niece is sitting in her room with the door open, and I wasn’t anxious to parade myself before her in my night clothes, I came down by the back staircase.  I don’t know how in the world I came to overlook it, but I think you ought to know that there’s a way of getting into the picture gallery without using either the windows or the stairs, and that way ought to be both searched and guarded.”

“Where is it?  What is it?  Why in the world didn’t you tell me in the first place?” exclaimed Narkom irritably, as he glanced round the place searchingly.  “Is it a panel? a secret door? or what?  This is an old house, and old houses are sometimes a very nest of such things.”

“Happily, this one isn’t.  It’s a modern innovation, not an ancient relic, that offers the means of entrance in this case.  A Yankee occupied this house before I bought it from him—­one of those blessed shivery individuals his country breeds, who can’t stand a breath of cold air indoors after the passing of the autumn.  The wretched man put one of those wretched American inflictions, a hot-air furnace, in the cellar, with huge pipes running to every room in the house—­great tin monstrosities bigger round than a man’s body, ending in openings in the wall, with what they call ‘registers,’ to let the heat in, or shut it out as they please.  I didn’t have the wretched contrivance removed or those blessed ‘registers’ plastered up.  I simply had them papered over when the rooms were done up (there’s one over there near that settee), and if a man got into this house, he could get into that furnace thing and hide in one of those flues until he got ready to crawl up it as easily as not.  It struck me that perhaps it would be as well for you to examine that furnace and those flues before matters go any further.”

“Of course it would.  Great Scott!  Sir Horace, why didn’t you think to tell me of this thing before?” said Narkom, excitedly.  “The fellow may be in it at this minute.  Come, show me the wretched thing.”

“It’s below—­in the cellar.  We shall have to go down the kitchen stairs, and I haven’t a light.”

“Here’s one,” said Petrie, unhitching a bull’s-eye from his belt and putting it into Narkom’s hand.  “Better go with Sir Horace at once, sir.  Leave the door of the gallery open and the light on.  Fish and me will stand guard over the stuff till you come back, so in case the man is in one of them flues and tries to bolt out at this end, we can nab him before he can get to the windows.”