They were wasting time. Rose was anxious; she couldn't deny she was ecstatic that Pete and her mum had found each other again after all this time, but she was aware that this was hardly the time for reminiscing. They were in the middle of a war zone, and her parents were acting like love-struck teenagers. She didn't want to break them up, but she didn't see any choice.

Glancing over at the Doctor, she could sense he felt the same way too. Wanting to get moving, sorting this out, but enjoying the scene before him too much. Well, he would be if he wasn't staring out the window, his brow furrowed. Rose felt her stomach flip. He didn't know what to do. That terrified her; she thought she could always rely on him to know what to do. Whenever he lost confidence in himself it made her want to cry. She wanted to wipe those creases out of his forehead, wrap her arms around him and tell him she believed in him. She'd always believe in him.

Crossing the room to the window, she stood beside him, looking down at the trail of destruction the monsters were wreaking. It was strange; Rose had seen so much death and killing since she'd been with him, but this time it hurt more. She supposed it was because it was out on the streets, the streets of her world, her city, her life. Looking out across the city, she scanned the horizon, looking between the clouds of smoke and fires breaking out. There it was, her tower block. It was only just visible from here, other buildings got in the way. Home. Only it wasn't anymore. She'd told her mum that. She'd admitted it so long ago to Mickey, before she'd become the Bad Wolf. There was nothing left for her here anymore. Her home was with him, this strange man standing next to her, his hands shoved in his pockets. Nineteen years of her life had been spent in that grey tower block, in that flat with her mum. But living… that had only begun when she left and stepped into the blue box, finding herself light years from Earth.

As if he'd only just become aware of her presence by his right shoulder, the Doctor glanced behind him at where Jackie and Pete were talking in whispers. He gestured with tilt of his head towards them.

"Shouldn't you be enjoying the family reunion?"

Rose shrugged, still staring out the window. "They need some time alone." She looked up into his brown eyes. "Anyway. I'd rather be here."

He gave her the briefest smile before resuming his contemplation out the window. Rose hesitated for a long moment, scared to ask the question in case he didn't have the answer.

"What are we gonna do?"

His jaw tensed up and he replied in clipped tones. "Do you want the truth?"

Rose nodded.

He sighed. "I don't know. I really don't know." He looked across at her. "Any ideas, Miss. Tyler?"

He was joking really. But Rose did have an idea, just a small one. She was sure it was a stupid one, else he'd already have suggested it. He'd spent so long looking out the window that she was sure he had turned over every possibility inside his mind. But she had to suggest it.

"Maybe."

He looked at her again, surprise on his face, but interest too. He'd take her seriously, she knew that. He wouldn't laugh at her and tell her to stop being such a stupid ape. He'd listen.

"I was just thinking," she said tentatively, gauging his response from his face. "And tell me to shut up if I'm being stupid but…" She had to look away as she suggested it, her eyes resting on a fire just breaking out on the London Eye. The site of their first adventure, she thought. But now wasn't the time for reminiscing. She took a deep breath and finished her thought. "Couldn't the TARDIS help?"

He began shaking his head almost as soon as the words left her mouth. "No, she's not made for combat. She'd just a travelling machine, a spaceship. And not like Jack's."

Rose nodded. "Yeah, I thought so." Another long pause before she had the nerve to add the last part of her idea. "So not even the time vortex could help?"

"What do you mean?" Panic washed over his face.

She looked up at him, meeting his eyes. "You know what I mean." She found herself smiling. "I've done it once. I could do it again."

"No. No, Rose, I won't let you do it."

"Why not?" Rose demanded. "It worked last time, all I'd have to do is…"

"I said no!"

"There's no need to shout!" Rose snapped back. She looked down at her chipped nails. "Why not?" she asked in a quieter voice.

"It's too dangerous." He shook his head. "There's no guarantee it would work anyway."

"You're just saying that," Rose insisted. "You know it would work. I could destroy them all, I could…"

"It would kill you."

Rose shrugged. "So?"

He turned to look at her, his face incredulous. "What? Rose, don't even start talking like that."

"Why not?"

"Because… just don't." He lowered his voice and reached out for her hand suddenly. He squeezed it tightly. "What would I do if I lost you, Rose? What would I do without you? Just think about that."

Rose wiped away angry tears, tears of fear and upset and feelings of utter uselessness. Being the Bad Wolf was all she could offer up to save everyone. She felt completely powerless as Rose Tyler.

"Then what?" she asked in a small voice.

"I'll think of something," he said, as comfortingly as he could.

"Promise?"

He smiled and pulled her into a hug. "When have I ever let you down?" he asked her, whispering softly into her hair.

"Never," she mumbled in his jacket.

"Right then." He let her go and wiped a tear off her chin. "Now, I think I've got an idea. But I need to get some things. Ready?"

She nodded. "Always."

He wished he hadn't let go as readily. He should have held on tighter for longer. Because he had an idea, a very good idea, an almost foolproof idea. But it would mean letting her go forever. His Rose Tyler. And his question to her kept pacing through his head, and he didn't have an answer for it. What would I do if I lost you, Rose? What would I do without you?