Melissa looked at the artificial heart in my hand with an expression of puzzlement in her chubby face.

"Why do I need that, daddy?" she asked as I let her hold it.

"So I can listen to it when I hug you," I said with a smile.

"What does it do?"

"It pumps blood and oxygen all over the body. I couldn't be alive without it."

"But I can, right?"

"Right."

"So why do I need it?"

"I told you. I want to hear it," I gently touched her chest. "In you."

"Why?"

I smiled. Just like a child, I thought.

"C'mon. Let's get you ready."

I passed my arm beneath Melissa's little thighs and lifted her up, carrying her to the next room as she distracted herself with the heart, feeling her fingers on the spongy surface.

"It's funny," she muttered to herself.

I gently laid her down on the metal slab. She sat back up, still examining the heart.

"No, no," I said. "Lie down."

She obeyed. "Sorry, daddy."

"It's okay, darling," I replied quickly, regretting the rudeness.

I reached out for the heart. Melissa smiled and gave it back to me.

"Now," I said, "I'll have to switch you off for a while, okay?"

A hint of fear showed in her big eyes. "Just for a while?"

"Just for a while."

"So I'll have a heart when I wake up?"

"Yes."

"So I'll be human?"

It wasn't the first time she asked that, and as usual I felt a wave of guilt upon hearing it. And like always, I had no idea how to reply. So I didn't and just smiled in a daddy-knows-best kind of way, leaning forward to caress her cheek.

"See you in a bit, okay?"

"Okay, daddy."

"Melissa oh-five-two."

Her eyes closed and her small body relaxed on the slab. It always bothered me, how terribly sudden that looked. For the thousandth time, I made a mental note to program a yawn in her code or something a little less scary than just switching off instantly.

I unbuttoned her blue dress and grabbed the cutter. It looked like the handle of a knife, but without the blade. I switched it on and a laser beam projected itself five inches from the handle. Far too long. I rotated a small button and lowered it to one inch.

On her chest, I drew a circle with the cutter. It was so precise I couldn't see anything different on her skin at first, but when I gently pushed it down the circle gave in and fell inside her body. I inserted my hand in, grabbed the edge of the circle and pulled it out through the hole. After scraping the fake skin off the circle, exposing the metal, I laid it aside on the slab.

I was glad to see the incision hadn't damaged anything else. I carefully probed the maze of wires in search of a red one. The red ones were connected to the internal computer -- her brain -- and I had left one or two unconnected spare wires for easy rerouting. I found one and pulled the unconnected end out of the hole to take a good look at it.

The end of the wire went into a plastic plug, which was inserted in a receiver on the heart. Then I went to my notebook and opened the "Melissa" software, which quickly connected to her A.I. code.

I wrote a line of code that used Melissa as an electricity source, and I switched it on. As programmed, the heart began pulsing on the slab and emitting a faint but audible beat. It was a little clunky. It didn't look or sound like the real thing, but it was close enough. It wasn't intended to function like the real thing anyway, just to resemble it.

I spent the next hour and a half writing code, so the heart would beat differently when combined with her programmed emotions. I briefly thought about making it beat faster when she lied, but then I remembered lying was completely absent from her programming. I asked myself why. She was, after all, supposed to be human.

I pushed the question out of my mind for later consideration and finished the last line of code. Carefully, I switched the heart off so it would switch back on with Melissa. Then I placed it over the metal circle I'd cut out of her chest, and I grabbed a plastic sheet. I stretched it over the heart, and taped the sheet's corners to the metal circle, safely involving the organ so it wouldn't be lost within her body. I briefly chuckled at the idea of finding the heart in her foot if I didn't use the plastic sheet.

It now looked like a plastic bag sealed by a metal circle, containing a heart and a wire snaking out of it. Worst of all, it looked ridiculous and not scientific at all, but I wasn't looking to win any prizes. So I just fit the circle back in the hole and, careful not to let the increased weight pull it back inside, I sealed it with a micro-blowtorch and laid a layer of fake skin over it, carefully sewing it to the pre-existing tissue.

When I was finished, it didn't look as smooth as I'd hoped -- it was like a scar, but not entirely unpleasant, and worth the sacrifice.

Anxious to see the results, I said, "Melissa oh-five-two."

She went from what seemed like deep sleep to totally awake in a milissecond. For the thousandth-first time, I told myself to program something to fix that.

"Do I have a heart now, daddy?" she asked.

"Let's see," I said, and laid the side of my head on her chest.

Steady as a metronome. So steady it seemed unnatural, but it would do.

"Yes," I said smiling.

"So?"

"So what?"

"You didn't answer me. Am I human now?"

I mentally cursed her memory chip.

"Well..." I said, groping for words.

And finally, I found a few, and sat on the edge of the slab. Expecting my reply, she did the same, her little legs, unlike mine, a long way from touching the floor.

"You already are human, Mel. You have been human since you put together your first sentence. When I first made you, you only spoke predetermined lines. As your code became more complex, you started being capable of analysing situations, coming up with sentences of your own -- capable of thinking."

"But you don't need programming, do you?"

"Of course I do. It's just not the same language as yours."

"Don't be silly, daddy. Humans are not programmed."

I caressed her hair, smiling. "We're machines, just like you. Organic machines, but machines nonetheless. The very act of laughing is programmed to certain situations. It's just that our programming is very complex. It comes from many years of evolution, and yours -- from an old fart with too much time in his hands."

She giggled. "You're not an old fart, daddy."

I smiled at her. "To me, you're a human two point zero, Mel."

I brought her closer to me and she hugged my chest like she'd never let go.

"C'mon," I said, picking her up and carrying her to the bedroom. "Time to sleep."

"I just slept!"

"I haven't."

As I gently laid her on the smaller bed next to mine, Melissa said, "Can't I sleep with you?"

I chuckled. "Of course you can."

We laid down in my bed and she rested her head on my arm, hugging me tight.

"I love you, daddy."

Of all the flaws in her code, this was one thing that she always said with perfection. More sincere and heartfelt than I, with my complex organic code, could ever be.

"I love you too, darling," I said, case in point. Still, I meant every syllable.

And then her sleep code kicked in. She didn't switch off, she just went into a believable simulation of sleeping. She could be woken up just like a real child. I cursed myself for thinking that -- she was a real child. Not like one. She was one.

But a real child who didn't actually need to sleep, or eat, or drink, or go the bathroom -- or die.

And I did.

I had considered the idea before, but it scared me. I never allowed myself to give it as much thought as it deserved. But now, feeling her heartbeat in my hand, it was stronger than ever -- the notion of something happening to me. An electric shock, food poisoning, a heart attack, a radiation leak from the outside world into the vault.

Melissa eternally alone.

A being I created to love me, suddenly losing me and the whole meaning of its existence.

No. She was more than just a thing to love me. I meant it when I said it -- she was a human 2.0. Loving, caring, capable of thought and emotion. With a little more work I could give her more complicated code, maybe even the ability to create art, but without the flaws of human nature. One could say you need those flaws to create art -- but maybe she could just understand them, without ever being a victim to them. Two point zero, as I said.

But the cruelty of it was more and more obvious to me the more I thought about it. I was developing a sentient being, bringing it into a small vault shielding us from a destroyed world where the one thing it could cling to was my fragile self. I would die and she wouldn't. I was damning her to an eternity of being alone.

And for what? For me. Because I didn't want to be alone in the few years I had left, trapped in what could be the last place on Earth that didn't require a hazard suit to keep you alive.

The scientist in me thought of ways around it. Maybe I could link my pulse to her computer, and when I died she'd switch herself off. Or maybe I could give her the means to do it to herself.

But in case those failed, I wouldn't be around to fix it. Maybe the link would fail, I'd die and she'd keep living. Maybe if I gave her an auto-shutdown program, she'd never use it, incapable of committing the robot equivalent to suicide.

After all, when I switched her off, she knew I'd switch her back on again. Without me, would she ever have the courage to do it?

I created a being capable of love, emotion and thought. But I couldn't create a world for her that went beyond me.

And she deserved so much more.

I took a deep, pained breath, feeling her heartbeat against mine, one last time.

"Melissa oh-five-two."

#  #  #

Submitted for the 11/09 challenge, "Heart."

This story was written in response to the prompt, Melissa looked from the gaping wound in her chest to the still-beating heart in her hand, and said, "Fuck."