Chapter 1

A few days before Christmas, I was curled up in the corner of the basement, wearing an old T-shirt my sister Colette had thrown out last summer. I didn't have socks. My feet had gone numb hours ago.

But there was a photo in my pocket.

A woman holding a newborn, smiling so hard her eyes crinkled. On the back, in faded ink: My little Nell.

The woman was my mom, Diane. The baby was me.

That was before Dr. Harmon.

Colette and I are twins. She was born sick and stayed sick, and Dr. Harmon told my parents it was because I'd stolen her immune system in the womb. I took what was hers. I owed her a life.

Dr. Harmon lost his license years ago. But by then his diagnosis had already sunk into this family like rot into wood.

They called it balance. Every time Colette got sick, I had to hurt the same amount, or worse. That was how the stolen things got paid back.

They'd been running that rule for seventeen years.

Upstairs, Colette sneezed. Small and delicate, the way she always did.

Mom's voice went off like an alarm. "Baby! Are you running a fever again? Turn the heat up, all the way!"

The basement door swung open.

Dad — Warren — came down the stairs with a brass padlock in his hand. He looked at me like I was a stain on the carpet.

"Colette has a fever," he said. "You know the rule."

"Dad." My teeth were chattering so hard I could barely get the words out. "I'm really cold. Can I have a blanket?"

"Colette's upstairs under three comforters and she's still shivering. What makes you think you get a blanket?" His voice didn't rise at all. "You haven't paid her back yet. You can freeze."

He hooked the padlock through the latch and twisted it shut.

"You come out when her fever breaks. Not before."

The door slammed. The lock clicked into place.

Then the dark swallowed everything.

I hadn't eaten in three days. My stomach had stopped cramping a while ago. Now it was just empty and numb, twitching every so often to remind me it was still there.

I crawled toward the old mirror in the corner.

It was a full-length mirror the last owners had left behind, split by a long crack that ran from one corner to the other. The glass had yellowed, but it still held a shape.

The crack cut my face in half. On one side my cheekbone stuck out. On the other, my eye had sunk into its socket.

"Is anyone there?" I pressed my forehead to the cold glass. My voice came out so thin I could barely hear it myself. "Somebody help me."

The silver behind the glass started to ripple.

Black smoke seeped out of the crack, thickening, curling, until it took a shape on the other side.

A tailcoat. A face I couldn't make out.

The Merchant.

I'd met him once before. Last winter, when my fever hit a hundred and seven, I traded three days of my life for a single pill and swallowed it dry on the basement floor. That was how I made it through the night.

"Poor little girl," he said. His voice came out rough, with an echo behind it. "Calling on me again. What do you want this time?"

"A warm blanket," I said. "And a piece of bread."

"Such a small wish." He let out a soft laugh. "And what are you planning to pay with? You don't have much left."

There was nothing in my pocket but that crumpled photo. Somehow my mind went straight to my own body.

"Can I use years?" I asked. "Or my health. They all say I stole my health from Colette anyway. Giving it back shouldn't be a big deal."

A few seconds of silence.

"Done."

He snapped his fingers on the other side of the glass.

The pain tore through my lungs with no warning at all. Blood came up my throat and hit the mirror, running down along the crack in two thin lines.

But at my feet, two things had appeared.

A thick wool blanket, folded neatly. A paper bag, and inside it a loaf of bread still warm enough to smell the butter.

I threw myself at them.

The second the blanket went around me, the warmth soaked through my skin into the muscle, then all the way into my bones. My fingers started to prickle and burn as the blood came back.

The bread hit my stomach and it cramped hard, then settled. Butter melted on my tongue, salty and rich. I chewed fast, my jaw aching, terrified it would disappear if I slowed down.

My lungs hurt. Every breath pulled at something in my chest.

But I was full. And I was warm.

It was the best moment I could remember.

"Five years off your life," the Merchant said, his voice already fading. "I hope there won't be a next time."

The mirror went back to normal. The blood dried in the crack and turned dark.

I sat down against the glass and pulled the blanket tighter.

Piano music drifted down from upstairs.

That was my brother Caleb. Colette loved hearing him play "Clair de Lune," so he played it every time she wasn't feeling well.

The music didn't cover their laughing. Dad said something. Mom answered. Colette whined about something in that sweet voice of hers, and Caleb cut in here and there. Four voices, wrapped up in central heating and firelight, coming down through the ceiling and landing right on top of my head.

I took the photo out and ran my thumb over the words on the back, there in the dark.

I rolled over and pushed my face into the blanket.

At least tonight, I wasn't going to die.

The lock came off around noon the next day.

Caleb stood in the doorway with his hands in his pockets, looking as annoyed as ever.

"Colette's fever broke. Mom wants you upstairs to clean the kitchen." He wrinkled his nose and took a step back. "God, what is that smell? Take a shower first. Don't come up smelling like that around Colette."

I didn't answer. First I folded the blanket and shoved it down to the bottom of an old cardboard box in the corner. If they ever found it, it would be in the fireplace by the end of the day.

Then I put a hand on the wall and started up the stairs.

It wasn't a long staircase, but I had to stop halfway and catch my breath. The pulling in my lungs was worse than the night before. Every breath made my chest lock up.

That was the price of the trade.