The Doctor swore and leapt up, pacing the library. She couldn't have just disappeared; there had to be a logical explanation. He ran his hands through his hair in frustration. He was missing something, something...

He scanned the area where she had been with the sonic screwdriver. Nothing. Not even residual energy to indicate transport of some kind. The TARDIS hummed in consternation.

"I know, I know!" the Doctor shouted back, increasing the speed of his pacing. "This shouldn't happen; she can't have just vanished. There's got to be something else!"

The TARDIS hummed louder, her telepathic link nagging at his mind. It was about the equivalent of someone tugging at his sleeve.

"What do you want me to do?" he snapped. "I didn't do this on purpose, you know! I'm trying to bring her back, I just don't know how!"

"Talking to the TARDIS. It has to be you."

The Doctor whipped around and dropped the sonic screwdriver. Rose was standing in the entrance to the library, clutching at a bookshelf for support. She smiled at him weakly.

"Is this another dream, then? Did she put me inside another dream?" She lurched toward him, and her knees buckled. Finding his feet, the Doctor lunged to catch her.

"I can touch you," she whispered. "If this is a dream, it's wonderful."

"It's...it's not," the Doctor stammered, sinking to the floor with her in his arms. "It's not a dream, and I don't know how it isn't, but it isn't, Rose, it isn't..."

She buried her face in his chest and he rocked her, holding her as if he could never let go again.

"Promise?" she said at last, peering up from the safety of his arms. "Promise it isn't a dream?"

"I promise, Rose," he answered, brushing the hair from her forehead. "I'm real, and so are you. You're here. You're back."

Rose dropped her eyes, thinking furiously. "She...she sent me back."

"What?" The Doctor dragged his attention from the wonderful, impossible vision of Rose's tear-streaked face and actually listened. "She?"

"Martha!" Rose cried. She slid out of the Doctor's embrace and stood, panic written in every line of her body. "She took it from me, the power of the Wolf. Our minds had touched, and it bled into her. She took it from me, all of it, and then..."

She stared at the floor as if trying to remember. "The Void. She used the Wolf to push me through the Void. The TARDIS must have pulled me in."

The Doctor shook his head. "It can't be. That...that would kill you, Rose."

Rose met his eyes. "She took my place, didn't she?"

There was a long, tense silence. The Doctor stared at Rose, and she stared back, but despite some intense mental acrobatics, the Doctor couldn't come up with another explanation.

"Rose," he asked quietly. "How powerful is the Wolf?"

"I don't know," Rose whispered, tears welling up in her eyes. "Powerful enough to destroy a universe. Is this such a stretch?"

The Doctor shrugged. "There's no precedent. Nobody has ever done what you did. I have no idea what that kind of power can or cannot do. Martha's gone, and you're here..."

He leapt up and began pacing, raking his hands through his hair. "You brought Jack back to life when he was dead, and you reduced the Daleks to atoms. Think, think! If Martha absorbed the energy, absorbed whatever you were, are, then she could do the same things, she might have...she could have...Rose, that's it!

"What's it?"

"You said it: she took your place. She's holding the power of the Wolf. She used the power to send you back here, because the universe was falling apart because of the intrusion of your paradox. Here, though, you're still a paradox, but a safe one, because the Wolf was formed from our time stream!"

"But the Wolf is still there, in that reality," Rose said softly. "They're still dying."

"I know. I know," he said, taking her hands and looking into her eyes. "But now I know how to save them."

She could feel the universe collapsing. Its endless gyre was closing in on itself, closing in on her; time was unravelling, and to stop it, space was going to collapse into a black hole with her at the center.

Through it all, Martha burned.

She'd done it; she'd pushed Rose through the Void. With that terrifying energy, she'd burned a hole from one world to the next and decimated them both to atoms, changed their places, and rebuilt them.

It had hurt.

But she had done it. The fires raged and the universe swallowed itself whole, but she had made a way for it all to end. She just hoped that Rose could figure it out in time.

I need you, Rose, Martha thought, and even the thought burned gold.

They lay close together, touching as much as they could. He lifted a hand to her temple and paused, frowning.

"I never said it."

Rose smiled up at him. "It's okay. I know."

"No, no, it isn't. I want...I want to say it. In case I don't have another chance." He drew in a deep breath. "Rose Tyler, I...I love you."

Her smile widened. "Say it again."

"I lo..." His words were swallowed as she pressed her mouth to his. He groaned, drinking her in, and she melted into him, as if trying to fit under his very skin. For a moment, nothing else mattered; then, he pulled away.

"Time...there's never enough time."

"There would be, if you didn't waste it so much," she quipped, and settled her head on his shoulder, ready.

"Doctor? I love you, too."

"Rose," he breathed, and lightly touching her temple, he plunged them both into dreams.

Nothing existed but the flame. On and on it went, devouring time and space together, and Martha was at its center. Death was in the flame; death was the only recourse. She closed her eyes to die.

"Martha!"

A wave of hope entered her mind, fighting back the flame. She knew that voice... There had been a beach, where something terrible had happened... Why couldn't she remember?

"Martha..." Another voice, also familiar. A man, this time. His people were dead, she remembered, but he didn't die. He couldn't die. He changed. Remembering was so hard...

A hand slipped into hers, and Martha gasped. Her mind was filled with thoughts of Rose.

"Rose," she whispered. "You came back. You came back for me."

"I won't let you burn," Rose promised. The light was leaving Martha, draining into Rose. The fires were dying. Time stood still.

Then time flowed backwards, making everything that was broken whole again.

Rose spoke, her eyes bright with the power of the Wolf.

"Come. We will return together."

"She can't, Rose. She can't come with us." The Doctor's voice was somber. "She took your place, and if she leaves as well, the universe will continue to collapse. Her presence heals the paradox; without her, just ripping the paradox away... It would be like the universe bleeding to death. She's covering the wound you made, and because she's not a paradox, she can stay. She can save everyone."

The last of the power drained away from Martha and she stepped back.

"He's right. I remember. I read it in a book; the Wolf showed me. I can't go back."

"I don't want to leave you," Rose whispered. Her voice echoed, but her words were human, all Rose. Martha touched her cheek.

"Dream of me, sometimes."

She turned to the Doctor, and he pulled her into a tight hug.

"Martha Jones," he whispered to her. "You saved the world, the universe, and you brought her back to me. I can never thank you enough for that, you know. I'll never forget you."

Martha pulled back and smiled at him. "I'll never forget you, either."

Rose drew in a sharp breath. "There's not much time."

"I know." Martha embraced Rose and felt the heat of the Wolf beneath her skin. "I'm glad I met you, Rose."

Rose flared with light, and Martha stepped back for the last time.

"I'm glad I met you, Martha Jones."

"Goodbye," Martha whispered.

The light disappeared into Rose, and then everything went black.