It was maybe twenty minutes later that we took the document and a tape measure and went into Quentin's bedroom.

On the wall opposite the door into the room there was, left to right: a chest of drawers, a large mirror, a wardrobe -- odd since there was a walk-in closet opposite the window -- and then another chest of drawers.

I unrolled the document. It was a diagram of the condo, showing all the rooms, electrical outlets, plumbing -- everything. And for each room dimensions were given for each built-in feature, such as doors and windows.

I examined what was written for Quentin's bedroom. Horst took the end of the tape measure and went to the left-hand end of the wall we were considering. Murmuring, "four feet, two inches," I pulled the tape to the right until I had the distance indicated from the left-hand corner.

It was just inside the left-hand frame of the wall mirror.

"Aha," I murmured.

Horst let go the tape and joined me in front of the mirror. I squatted down. The mirror's bottom was a foot from the floor, six inches above the top of the lower molding. I ran my finger along this, from behind the chest of drawers on the left to as far as I could reach behind the wardrobe. Then I looked up at Horst.

"There's no break. It's continuous."

"Huh."

I stood up, and examined the mirror. Grasping it on either side -- it was about three feet wide and five feet high -- attempted to lift it.

Nothing happened. I tried a bit harder, and felt only a slight give. So I gave up and letting go, stepped back.

"Okay," I murmured. "Something --"

Horst had moved forward and was running his hand along the left side of the mirror frame.

"Anything?"

He shook his head, then paused, and -- click! The left-hand side of the mirror swung forward, like a bathroom mirror on a medicine cabinet. He pulled it wide, and exposed --

Nothing.

It was just wall, unbroken, and unmarked. The pale blue wall was unblemished, though it was just slightly darker within the rectangle where the mirror rested -- no doubt due to the slight fading of the exposed wall surface.

Horst looked at me, and I looked at him. We both laughed.

After staring at the spot, I stepped forward and began running my fingers over the surface of the wall. At last, I stopped. I had found -- something. I stepped closer still and examined the wall where my fingers were. There was a slight, ever so slight, irregularity, which ran in a vertical line an inch to the right of were the unfaded wall color began.

I ran my fingers along this, and gradually felt out what was clearly a rectangle, smaller than the mirror, of slight discontinuity. Convinced that this rectangle must in some way be movable, I hesitantly pressed into it, near its left side.

There came another click, and the rectangle of wall swung open just as the mirror had. Taking hold of this, I pulled it wide open -- and found myself looking through the rectangle at what appeared to be an ordinary room.

Horst and I looked at each other, eyebrows raised. Then I gestured for Horst to be the first to enter. He hesitated, but then stepped through -- the bottom of the opening being just over a foot above the floor, something like the doors in submarines. I followed.

It was clearly a study -- Quentin's inner sanctum!