A.N: I've recently watched a marathon of the Sarah Jane Adventures and Primeval, then decided to do my own interpretation of why Claudia Brown vanished. Nick and Helen remembered her because they had been on the other side of the anomaly, so they weren't affected. In this case, they work in a similar way to the Puzzle Box that Maria had.

Disclaimer: I don't own Sarah Jane Adventures or Primeval.

Nick had stepped through the anomaly a little while ago and Claudia was getting worried. She wondered absently, what her sister would do if she were here.

None of the rest of the team knew about her sister. Her twin sister. They'd been completely identical, only her hair was lighter than her sister's dark brown. Her sister had died a long time ago. She barely remembered it. She'd been hit by a car.

Her sister had been full of life, headstrong and independent, social and smart. She was clever in a dangerous way. And Claudia missed her.

And while she was wondering and missing her, Claudia Brown vanished from existence.

Many years ago…

Jennifer Lewis sighed as she sat on the park bench, arms folded as she pouted. She hated this new court agreement, that she was in the care of their Mother, while her sister was in the care of their Father. It wasn't fair! She wanted to live with Claudia, not either of them. And if that wasn't bad enough, they'd changed their names so now she was Jenny Lewis, but Claudia was Claudia Brown.

"Why so blue, Twin Two?"

Jenny looked up with a beam to see her twin sister, Claudia's hair a little lighter than her own.

"Without you, no fun, Twin One," she replied standing up and hugging her sister.

Claudia laughed and grabbed her hand. "Let's play in the tunnel!"

The younger twin shook her head. "Nuh uh. Let's go on the big slide."

Ever the less daring twin, Claudia bit her lip. "We're not s'posed to," she mumbled.

Jenny rolled her eyes. "Mummy and Daddy aren't looking," she said, putting her hands on her hips. "It'll be fun." She smirked. "Tell you what, let's leave."

"What?" Claudia gasped.

"Let's leave," Jenny repeated. "Let's go so that we never have to be split up."

Shaking her head, Claudia folded her arms. "No way! We might get hurt or taken. I'm not running away."

Jenny rolled her eyes again. "We'll be fine," she snorted. "I'll look after you if you're scared."

"I'm not scared!" Claudia protested. "Come on, let's go."

She strode out, Jenny smirking before running after her.

By the time either of the adults looked up from their phones, the twins had long gone, the park otherwise deserted.

The missing twins were running down the road, Jenny ahead of Claudia, both laughing at the unexpected freedom.

"Jenny!" Claudia called, tripping slightly on her laces. "Slow down!"

"Hurry up Claudia!" Jenny called back, running faster than before. "Slow poke!"

"Jenny!" Claudia cried again, her pace slowing even more as she began to run out of breath. "Jenny, wait!"

"Come on!" Jenny yelled, turning her head to look at her twin, not paying attention as her foot left the pavement and she ran into the road.

Claudia screamed as a car horn blared and breaks squealed, Jenny swinging round, her hands flying up in front of her face seconds before the silver Skoda hit her and everything went black.

Jenny lay on the road, staring up as Claudia's mouth moved, talking frantically but no words sounding in Jenny's ears. Everything hurt. Everything.

A voice suddenly echoed from nowhere, no body, no speaker, just a voice.

"Jenny, you don't have to die. Somebody has to die, it doesn't have to be you. Let her die in your place."

In her young, fogged state of mind, Jenny didn't really register what the voice was saying, only that she would live. "Yes," she whispered, "Yes."

And then suddenly it was Claudia on the ground, broken and battered, blood coming from her ear. "No!" She screamed. "Claudia! Claudia!"

She fell to her knees, speaking frantically, begging her sister to be okay. Tears ran down her face as she screamed her throat raw.

"Please! No!"

But it was too late.

Jenny hated Nick Cutter. Well, she didn't hate him. Just that he called her Claudia. She should have told him that Claudia Brown was dead, she really should have, but at first she was too angry, then he was too distant, then it was never the right time and eventually it was too late. Slowly she fell in love with him, but never acted upon it, too guilty over her lies. It was odd, hating and loving a person at the same time. When he died, a part of her seemed to die too.

She found the picture of him and Claudia, snippets of an agreement from years ago surfacing in her mind. She could have cried. But she lied to Sarah, lied that she used to be somebody else. She knew it was her sister, her bubbly, full of life sister. She knew what she did to her sister and she hated it.

So, she left, unable to cope with the memories, the memories of her long lost twin. And the memories of what she had done. She got away, moved somewhere else, started a new life for herself and forgot Claudia Brown as best she could.

Seeing the ARC team again dragged it all back opened, opened closed wounds. She lied to her fiance, told him she used to be Claudia Brown, but later that night she told him the truth.

"I wasn't ever Claudia Brown," she told him softly. "I lied because they were watching and they don't know. I can't bear to tell them. Claudia was my sister, my twin. When we were little there was an accident. It's weird, what happened. I remember it two ways. The first, I was hit by a car. I died Michael. But there was a voice, and it said I could live. So I said yes. But suddenly Claudia was there, in my place. I hadn't realised what I'd agreed to. I agreed to sacrifice her for myself." She was in tears. "I agreed for her to die."

For his credit, Michael listened in silence and when she was done, pulled her into his arms wordlessly. Finally, Jenny let it all out and sobbed. She had never told anybody what she had done and she had never intended to. But in the end, she needed to.

Claudia Brown had lived a life, a short life, only for a single word to wipe her from existence. A mistake that cost one life, but saved another. She was never really forgotten.

And Jenny? Her only daughter was called Claudia Nicole.

Claudia Brown was never supposed to die.
But a single word wiped her from existence.
And Jennifer Lewis survived.
All it took was one word.