There was nothing out of the ordinary anywhere, and so I assured Mrs. Klopton.  Needless to say, I did not tell her that I had left the trap-door open, to see if it would improve the temperature of the house.  I went to bed at midnight, merely because there was nothing else to do.  I turned on the night lamp at the head of my bed, and picked up a volume of Shaw at random (it was Arms and the Man, and I remember thinking grimly that I was a good bit of a chocolate cream soldier myself), and prepared to go to sleep.  Shaw always puts me to sleep.  I have no apologies to make for what occurred that night, and not even an explanation that I am sure of.  I did a foolish thing under impulse, and I have not been sorry.

It was something after two when the door-bell rang.  It rang quickly, twice.  I got up drowsily, for the maids and Mrs. Klopton always lock themselves beyond reach of the bell at night, and put on a dressing-gown.  The bell rang again on my way down-stairs.  I lit the hall light and opened the door.  I was wide-awake now, and I saw that it was Johnson.  His bald head shone in the light—­his crooked mouth was twisted in a smile.

“Good Heavens, man,” I said irritably.  “Don’t you ever go home and go to bed?”

He closed the vestibule door behind him and cavalierly turned out the light.  Our dialogue was sharp, staccato.

“Have you a key to the empty house next door?” he demanded.  “Somebody’s in there, and the latch is caught.”

“The houses are alike.  The key to this door may fit.  Did you see them go in?”

“No.  There’s a light moving up from room to room.  I saw something like it last night, and I have been watching.  The patrolman reported queer doings there a week or so ago.”

“A light!” I exclaimed.  “Do you mean that you—­”

“Very likely,” he said grimly.  “Have you a revolver?”

“All kinds in the gun rack,” I replied, and going into the den, I came back with a Smith and Wesson.  “I’m not much use,” I explained, “with this arm, but I’ll do what I can.  There may be somebody there.  The servants here have been uneasy.”

Johnson planned the campaign.  He suggested on account of my familiarity with the roof, that I go there and cut off escape in that direction.  “I have Robison out there now—­the patrolman on the beat,” he said.  “He’ll watch below and you above, while I search the house.  Be as quiet as possible.”

I was rather amused.  I put on some clothes and felt my way carefully up the stairs, the revolver swinging free in my pocket, my hand on the rail.  At the foot of the ladder I stopped and looked up.  Above me there was a gray rectangle of sky dotted with stars.  It occurred to me that with my one serviceable hand holding the ladder, I was hardly in a position to defend myself, that I was about to hoist a body that I am rather careful of into a danger I couldn’t see and wasn’t particularly keen about anyhow.  I don’t mind saying that the seconds it took me to scramble up the ladder were among the most unpleasant that I recall.