Author's notes: I'm a little surprised I'm writing this story. I expected myself to chicken out. I'm glad I'm doing it though. It's my first true Vincent-centric fic and so any input would be much appreciated.
This story was originally meant to be a song-fic to a French song called Un monde à l'envers by Bruno Pelletier but, like Mementoes, I ran out of story before I ran out of lyrics. So, here it is, sans lyriques.

Monster

It was raining. The raindrops caressed the abandoned mansion's rooftops and windows making soft, whispering noises in the emptiness. One man's footfalls echoed alone in the hallways. Lightning brought a sudden shocking illumination to his surroundings and for a moment his eyes glowed red in the darkness.
Thunder sounded moments later shattering the illusionary silence. The man tensed and stopped, listening. The thunder faded and he was alone again. He continued walking.
Eventually, his feet took him into the mansion's dinning room. Memories floated up around him. There had been a woman sitting by that window, reading. She had smiled at him timidly and he had returned the gesture. He had watched her playing the piano softly and had chuckled at her frustration when a few notes turned sour. There had been others too: men with great dreams and terrible ambitions but mostly he remembered the woman.
Alone, the man walked over to the windows. Dust had settled on the panes and the furniture was covered with pale white tarps. One hand reached out to touch the bare window's glass. He had kissed that woman here, right here. Foolish and dangerous, being out in the open like that, but she had looked so very beautiful in the moonlight and...
The man's other hand clenched at his side and a strange metal-on-metal tinkling echoed in the empty room. A woman's name died on his lips. The man cringed and pressed his forehead against the window. Something was wrong. He felt, he felt...
A terrible pain ripped through his body and the man fell the to ground, trying not to scream. What was this? He was...
Lightning crashed illuminating the room. The man caught his reflection in the window just for a moment melting, fading, changing...

The man woke up. For a moment, he couldn't remember who he was. There had been someone – something – else. There had been fire and claws and... The man sat up and held his head in his hands.
No one must stand in the way of my research. Not even you, Mr. Valentine.
Valentine. Vincent. That was his name. Vincent Valentine.
Vincent raised his head and looked at his hands. There had been fire and claws. That's what he had: a metal claw. Memento.
Vincent doubled over, his body protesting in pain. He was retching painfully, his stomach trying to rid itself of something. He could taste something vile in the back of his throat. Vincent couldn't see it but there was a tiny splash of blood a few feet away from where he was sitting.
Eventually, Vincent's stomach gave up and he lay back down on the cool floor of the dinning room.
A monster, he thought, closing his eyes. She had flung that name at him once in anger and pain. Now her words echoed back at him. He was a monster, a monster.
"Lucrecia," Vincent whispered.
It was coming back to him now. Hojo. The experiment. Lucrecia. She had... fallen. And he had run for help. But Hojo, he had turned on him. He had never expected the gun. And then there had been... a table. And pain. Oh God.
Feeling shaky and drained, Vincent pushed himself up from the floor. He took a few steps forward towards the wall but stumbled. He caught himself and rested by the room's window. That was when he noticed the long trail of blood that was trickling down his right arm. He must have cut himself somehow. Again, he considered the metallic claw that now replaced much of his left arm. Looking at it was making him dizzy. He tore his eyes away and looked at the window. His hand had left a bloody imprint on it. He stared at it with a morbid fascination. She had bled so much too, near the end.
The memory jolted him out of his reverie and he took a hasty step away from the window and from his own smeared blood. With wild eyes, he searched around the empty room, almost as if he could find her there.
And just like that it was suddenly too much to bear. He could remember everything now. She had stood here waiting for him at night. She had raised her beautiful face to his and had smiled and kissed him. She had, she had...
She had spun away from him in fear and confusion and in his folly he had let her go. He had watched her flee into another man's waiting arms. In the dead of night, they had carried out their affair but with Hojo she hadn't needed to hide. Vincent had walked through the mansion and had seen her holding his hand, smiling at him, kissing his face. Sometimes, she had looked over at him with empty eyes. At night, God help him, at night... her child needed a father, she had told him.

Vincent's shuffling feet carried him away from the dinning room and up the empty stairwell. He walked into the bedroom close to the greenhouse that Lucrecia had tended so devotedly. Here, it had been right here. For so long he had avoided her, determined that he was doing the right thing. For her, he had become even more distant, even more aloof. After the birth, the child's mother had been completely forgotten and had soon become sick. Mako poisoning, Hojo had pronounced so callously. At night, Vincent had crept into her room. She had been half-mad, calling out for her son. Then, she had collapsed. Vincent had run to the basement to find one of the doctors but the others had all left. Only Hojo had remained behind.
Vincent looked down at his metallic claw again. Surely this was his punishment. Now he finally was the monster he had always been.
Soft laughter seemed to rise up around him.
"Lucrecia?" Vincent called. He winced in pain and touched his good hand to his temple. God his head hurt. The sweet laughter faded away and Vincent was left alone in the room again. Then, he thought he heard his name. Vincent spun around.
"Lucrecia?" he called again, more desperate. A rational part of his mind reminded him that Lucrecia was dead but he could have sworn he had heard her.
Vincent. There it was again!
"Lucrecia!" Vincent followed the voice out of the room and down the hallway. He paused when he reached the hidden door to the basement. A part of him didn't want to go down there. A memory flashed before his eyes: the blade of a knife, hovering above him inches away from his face. No one must...
Vincent.
Resolutely, Vincent pushed the hidden lever to open the door to the basement. The long stairwell was exactly as he remembered it. He had come down here occasionally while escorting the scientists to their work.
He walked down the empty hallways of the basement. There was a door open that he had never noticed before near the end of the hall. Vincent shied away from it though. Something about it bothered him. He walked instead into the library. All of Hojo's old machines were still there, dust-covered and sleeping.
Slowly, Vincent walked forward towards the bare wooden table in the middle of the room. Four metallic clamps were still arranged on it. His fingers reached out to touch one.
Cold metal biting his skin. Needles and wires. His own blood draining away, mixing with something and then returning to him but burning, sweet God, burning all through his body.
Vincent stumbled back from the table and clutched his hand to himself. He didn't want to remember.
He walked away from the room and closed the door behind him.
"Lucrecia?" he called again but now he was beginning to understand that she would not answer him, that she had never answered him.
Vincent paused at the new open door. He had never noticed it all the other times that he had come down into the basement. Against his better judgement, his feet carried him into the room. He gagged against the stench. It was some kind of crypt. There were a few coffins arranged up on a dais. One was open.
Wouldn't it be appropriate? Lucrecia was dead. Perhaps she was even lying in one of these coffins beside him.
Cautiously, Vincent walked up towards the open coffin. It was a simple wooden thing with no plush lining on the inside. Forgetting himself, Vincent reached out to touch its wooden contours with his left hand. The sharp metal of his claw scratched the wood. Vincent looked at what had once been his hand and closed his eyes. He could feel them in the back of his mind, watching. His punishment.
Slowly, Vincent lowered himself into the coffin. He'd sleep here amongst the dead.
Vincent pulled the lid of the coffin over himself. When the darkness consumed him, he felt a moment of panic, the last live part of himself struggling to win free. He crushed it resolutely and closed his eyes.
He waited for the nightmares to come.