Rose stood there for a second or two in shock, just staring. And the thing that looked like her just stared back calmly. It was exactly like looking at herself in the mirror. Then the Healdon's face – her face – twisted into a smile, and the spell was broken.

Rose turned and ran. The scream that she been stifling sudden erupted as a call for help as she tore down the corridors. She could hear the Healdon behind her… trainer-clad feet beating out a rhythm on the stone over the sound of her own.

She didn't know where she was going, but now that she was running the adrenaline didn't seem to want her to stop. The creature was catching her up; she heard the squeak of rubber as it turned the corner, metres behind her. She briefly considered facing it and hoping it didn't try to kill her, then was about to dismiss the idea when the decision was made for her.

The Healdon shoved her from behind and Rose was thrown off balance, her shoulder slamming into the wall. She cried out in pain then tensed herself, ready for combat, determined not to give up without a fight. But none came.

To her surprise the Healdon was now the one running away, and fast. Rose got up and followed it gingerly, keeping as large a distance between them as possible while she could still see where it was headed. She felt an intense sensation of deja-vu, and the thought crossed her mind that maybe, like the episode with "Jack" before, this was another ploy to get her on her own. The Healdon never once looked back.

Then the Doctor's voice came echoing down the corridor. Rose sped up, but ahead of her, the Healdon did the same as it turned the corner. She heard a "Where did you get to?" then the next second the passageway opened into another junction and she stopped abruptly as she was confronted with the pair in front of her.

The Doctor surveyed Rose and her lookalike. He didn't seem overly perturbed, Rose noted with frustration. She opened her mouth to speak, to tell him to do something, say something, just stop standing there, but the Healdon, barely two metres away, got there first.

"Doctor! Help me, it's her, she's pretending to be me –"

"NO!" Rose, with a shock, realised the Healdon's plan. "No, Doctor, look, it's me, Rose!"

"She's lying! I'M ROSE!"

"Doctor, don't listen –"

"Please, Doctor, don't you recognise me?" Rose felt sick at the sound of her own voice coming from the Healdon, whose tone had turned pleading.

"Doctor –" Both versions of Rose spoke simultaneously.

"Be quiet, both of you," the Doctor snapped suddenly, his voice full of quiet authority, silencing the pair. He walked towards them, stopping a few feet away.

"You can't both be Rose Tyler," he said, sounding vaguely amused, but his look remained deadly serious.

He glanced from Rose to the Healdon. Rose met his gaze, straining with all her being to convey her words through her eyes. She had been wary when she had first learnt of his telepathic qualities, but for once she wished he could read her thoughts.

"It's lucky I can tell the difference," the Doctor said calmly.

And without warning, moving so quickly that neither had time to react, he reached out and grabbed Rose's hoodie, yanking her forcefully towards him.

Taken by surprise, Rose yelped. She was glad her had chosen her, but he didn't have to be so heavy-handed, she thought. And then she realised.

"It's alright, Rose," the Doctor was saying. But not to her. He was speaking to the Healdon.

"I'll deal with her. Now, I need you to find Jack –"

"No! Wait!" Rose struggled against the Doctor's powerful grip.

"Quiet!" he said brusquely, his grip tightening, and his hand closed over her mouth, muffling her protests.

Rose stopped, tears pricking her eyelids. He'd never used that tone with her before, and it both frightened and upset her.

" – and go back to the Tardis," the Doctor was saying. The Healdon was smiling in relief, for once the emotion genuine.

Rose felt her anger rising. She couldn't – wouldn't – let this impostor steal her Doctor. She tried to protest, tried to wrench her arms from his grasp, but it was no use.

"Rose, go. Find Jack…" the Doctor hurriedly told the Healdon, who nodded and turned to leave. The Doctor pushed Rose hard, manoeuvring her in the opposite direction.

There was a door open to their left, and he bundled her through it roughly as she tried to resist. Rose landed on the floor of the small room beyond, not physically injured, but her feelings hurt.

The Doctor peered back through a crack in the door for a moment, watching as the Healdon turned the corner. Then he turned, and looked at her.

I do love leaving it on a bit of a cliffhanger! If you could call it that, lol. All comments gratefully appreciated... :-D