Two hearts.

Rose haunts her. Everywhere she turns in the Tardis, she is aware of Rose's presence, behind her, beside her, round the next corner, waiting for her. Rose's laughter echoes down the empty corridor, a flash of gold in the darkness is her hair. Even away from the Tardis, she thinks of the girl that came before. Wonders if he took her to this new world, or the next, and if he didn't, did he mean to? All day, all night, her thoughts and dreams are filled with Rose.

It wasn't always like this. Once she barely even knew who Rose was. Rose was just the name of the companion before her. He mentioned her once or twice, and a flicker of sadness passed behind his eyes, but that was all. Just another name. The latest in a long list of names that had started with Susan, and currently ended with her own.

Of course she fell in love with the Doctor. How could she not? A tall dark handsome stranger sweeps into her life, rescues her from the very vicious bad guys, and whisks her away from her boring, dull, stagnant life to adventure and planets and bizarre aliens. He was mysterious, and funny, and knew such a lot, and vulnerable and brave and had the darkest eyes, and she was not surprised when she fell head-over-heels in love with him.

She didn't expect him to love her back. She was fine with that. Sarah-Jane had warned her the Doctor didn't love ages ago.

"Well, he does love," Sarah-Jane had told her, in a Viennese café over pastries as the Doctor was arguing with Freud in the corner. "He feels very strongly about people, and his companions. He gets very fond of us. He just doesn't love in the way you and I know it. You know, monogamous, one-on-one, kissy, huggy, sex kind of relationship."

The new companion nearly choked on her pastry. She'd come from a much earlier time then Rose, and was consequently not quite as comfortable talking about sex as Sarah-Jane seemed to be.

"The first Doctor I met was quite sexy." Sarah-Jane reminisced, not noticing the blush spreading up her companion's face. "The second one – he was the fourth Doctor – well, I wouldn't call him sexy, although he was magnetic. Now the fifth Doctor – he was gorgeous, but I only met him for a few minutes. I didn't half envy Tegan, getting to go off with him. And your Doctor…" she glanced over to where he was passionately making a point to Freud, and illustrating it with a pastry fork. "Now he's a honey. But like I said before – fancy him all you like. Fall in love, I know you will. In any incarnation he's irresistible. But don't expect him to fall in love back."

The new companion looked down at her pastry, and muttered something.

"I know that look." Sarah-Jane said gently. "Trust me on this."

"He doesn't fall in love. I know." The woman said, looking at Sarah-Jane with brave, hurt eyes.

"He did once." Sarah-Jane mused. "Or at least, I think he did, because he has a grand-daughter. But now….."

The new companion accepted this. She was close to him, lived with him, saved him, and was protected by him, fought beside him. It was enough. And if ever she got lonely one night, Jack would always turn up. She'd seen the same look in Jack's eyes when he looked at the Doctor. She and Jack, knowing neither could ever have him, would console each other in bed, at night.

And life had been fine. But one night, she and the Doctor had found themselves locked in a prison cell for the night. And he had decided that escape might as well wait until morning, and had lain down and gone to sleep. She'd stayed awake, unable to sleep for some reason.

It had been silent, but warm in the cell, and she had been dozing lightly when she heard the Doctor speak. She opened her eyes, and looked across, but his eyes were still closed.

He had been calling out in his sleep. And the name he had called was 'Rose'.