I crept down the stairs of the old house, wincing every time the old boards creaked beneath my tread. My uncle was fast asleep, but I knew that he didn’t sleep heavily. What if he heard the noise and woke up?

Finally, after what felt like ages of moving with excruciating slowness, I reached the bottom of the stairs. I slipped a hand into the pocket of my pajama bottoms, curled my fingers around the brass key that lay inside.

The door to the library, seven feet tall, loomed in front of me. I looked up at it with trepidation, wondering how much trouble I risked getting myself into. After all, my uncle never failed to remind me, on each visit to his house, that the library was off limits. He kept it locked for a reason, he insisted, even if he never divulged that reason to me.

During the first few summers when I visited him, the question of what lay behind the library door never became much of an issue. The old, mouldering Victorian mansion where my uncle lived had many other secrets to uncover, and I delighted in ferreting them out.

I found the secret passages inside the walls, the ones that my uncle claimed had been used by servants to ferry meals to the lord and lady who once lived here. I discovered how to operate the dumbwaiter from inside the box, a little hand-controlled elevator to carry me up and down between the first and second floor. I even ventured into the attic, peering into dusty boxes left over from many years before – up until a bat swooped down on me, sending me running back to safety, shrieking my head off.

But I’d never ventured into the library. My uncle kept the door to that room securely locked, and I’d never found a passage leading inside.

I might never have thought about it at all, had I not uncovered the key. I found it in the back of the huge apothecary desk in the living room, taped to the backside of the drawer. One of the little drawers had been stuck, so I pulled it as hard as possible, yanking it all the way out. When I went to slide it back into place, I spotted the gleam of the brass key, hidden inside the back of the huge, hulking desk.

The key was made from ornately worked brass, with a large “L” engraved on the handle. I knew immediately what door it must open.

I had spent the last twelve hours in tortured uncertainty, debating whether to dare breach the trust my uncle instilled in me. But finally, my ten-year-old sense of curiosity overwhelmed my reluctance, and I crept out of bed and padded down to the library door.

The key fit smoothly into the keyhole, and I heard something click inside the door when I turned it. I withdrew the key and, my heart thumping so loudly in my throat that I could scarcely hear anything else, I reached out and laid my hand on the knob.

It turned. The door, heavy and sticking a little from humidity, finally gave way and opened outward. I slipped inside.

Darkness on the other side of the door overwhelmed me. My pounding heart grew even quicker, and I nearly panicked when my scrabbling fingers failed to find a light switch on the wall. It was too dark! I needed to leave!

I ducked out into the hallway once again, my heart still threatening to explode inside my chest. But the familiar hallway gave me strength, and I swore that I wouldn’t be defeated so easily. My uncle kept a flashlight in a drawer in the kitchen. It was the work of a moment to duck across the hall and retrieve it.

Now armed with my beam of light, I once again entered the library. I panned the flashlight around, taking in the shadowed interior. It looked…

…well, it looked like a typical library. I saw tall shelves rising up to the high, vaulted ceiling, covered in leather-bound volumes. A rail ran along the top of the bookshelves, and I found a ladder connected to it, on wheels so that it could slide along the shelves. A dark fireplace stood against one wall, and several old-looking leather armchairs and end tables stood scattered around the room.

I frowned, feeling a little let down. This was the forbidden library that my uncle didn’t want me to see? What was wrong with it?

The flashlight slipped a little in my fingers, dropping to aim its beam at the floor – but my eyes caught a faint glow still lingering above, up on the mantle of the fireplace. I frowned, brought the light back up, but saw nothing there. Had my eyes been playing tricks on me?

Curious, I slid my finger to the switch on the flashlight. After a glance over my shoulder, ensuring that the door still stood ajar so that I could make a quick escape if necessary, I flipped the switch. The beam turned off, drowning me in darkness.

But the darkness was only absolute for an instant. That glow returned, ever so faint but growing brighter as my eyes adjusted, a few inches above the center of the fireplace mantle. And as I watched, it swelled outward as a new shape appeared, gauzy and ephemeral, floating in the air.

The shape of a face…