The Doctor ran through the halls, turning down various corners.

"How're you holding up, Rose?" he called over his shoulder. "Rose?"

No answer. The Doctor skidded to a halt and spun around, looking back the way he came.

"Rose?" he yelled as he started to sprint down the long hall again in the opposite direction. "Rose where are you?!"

"I'm here!" Rose answered and then ran out from a side tunnel. "Let's go!"

The Doctor almost tripped over his feet because of how fast she ran by.

"Alright!" he laughed. "I guess you're gonna lead the way?"

"You bet!"

The two sprinted down the hall, passing by various cells and labs as they went on their way to escape.

"Take a left up ahead!" the Doctor called to his companion.

"Why?"

"Cos we have to free everyone else!" the Doctor frowned. He thought Rose knew that…

"We don't have time for them!" Rose barked. "Leave them behind!"

Okay. Something was seriously wrong with Rose.

"Stop! Stop stop stop," the Doctor reached out and caught her on the arm. Growling angrily, she let him pull her aside into a small corridor.

"What?!" she snapped, crossing her arms. "Why are we stopping?"

"What's gotten into you?" the Doctor countered.

"I don't know what you mean."

"I mean when have you stopped caring about the slaves?"

"Well when have you put them before my safety?" Rose glared at him.

"What?!" The Doctor's eyes widened. "I always put you first!"

"If that was true then we'd be back at your ship!"

"What? Rose, what, what's going on?" The Doctor furrowed his brow and looked her over. She stared back at his with cold blue eyes.

Wait. Blue eyes? Rose did not have blue eyes. She had the most beautiful hazel eyes.

"You're not Rose!" the Doctor growled and lunged forward pushing the imposter across the wall. "Where is she?!"

"I-I don't know what you're talking about!" she pulled at his hands trying to pry them off her collar. "It's me, Doctor!"

"I don't think so!" he snapped. "Last time I checked, Rose cared about people and had hazel eyes!"

"Rose" slacked against the walls, a grimace spreading across her face.

"Well, nobody's perfect, are they?" the woman's voice changed and her eyes flickered into a hazel color. "There. Happy now?"

"Where is she?!" the Doctor yelled. "What have you done with her?!"

"I'm right here," her voice switched back into Rose's. "Don't you believe me? Don't you trust me?"

"I trust Rose more than anything. Don't mess with me," he shook her roughly. "You tell me where she is right now!"

"Why?" the woman whined. "What's wrong with me? I'm so much better than that pathetic human. Besides, I don't even have to be 'Rose'. I can be anyone you want…"

The creature before him shifted, morphing into various companions he had had. Sarah Jane, Ace, Jo, even Jack to which the Doctor's eyes widened in horror.

"Stop it!" the Doctor yelled and banged the shifter's head against the wall, causing her to snap back into Rose's form.

"What's the matter, Doctor?" Rose's voice cooed. "Is no one good enough for you?"

"TAKE ME TO ROSE RIGHT NOW!" the Doctor latched his hands on her throat, digging his fingers into her neck. The shifter gasped for air, her skin rippling into green scales and her features changing.

"St-stop!" she coughed. "L-let me go! I—!"

"Tell me where she is!"

"No!"

"TELL ME NOW!"

"She-she's in a cell!" the creature cried. "5R! 5R!"

The Doctor released his grip on her throat and let her fall to the floor coughing and gasping. He didn't wait another moment before running out into the main corridor and toward holding area 5R. As he tore down the halls he could hear alarms blaring. The shifter must have recovered more quickly than he had hoped.

Taking a right, he skidded into a large room peering into each cell that lined the walls. All of them seemed to be empty, except…

"Rose!" The Doctor cried and ran over to where her crouching form was in the corner of a cell.

"Doctor?" she looked up to him, relief covering her features. "You're still here!"

"Course I am," he said as he punched in a combination to release her. "Wouldn't leave without you."

"But, that, that thing," Rose shivered. "She turned into me. Said she was gonna run off with you and—"

"No one can fool me by trying to be you," the Doctor smiled as the cell wall slid to the side. "You're one of a kind."

Rose grinned and threw herself at him, wrapping her arms around his neck in a tight hug. He returned her embrace whole-heartedly before gently unwinding her from him as a loud siren came over head.

Taking her hand in his he gripped it tightly and whispered, "Run!"