She awoke in a frozen sweat, trembling. Nauseous, disoriented, and colder than she had ever been in her life, and unable to see anything through the darkness surrounding her… Where was she? For a hideous moment she felt completely vulnerable and exposed. Then all at once memory came flooding back. Oh yes, the TARDIS medical unit. The Doctor. He had come for her.

"Doctor?" she said, but it came out a croaked whisper.

A cool hand clasped hers. "I'm right here."

"Co – cold," her teeth chattered as she forced the words out.

"I know. I'm sorry. It's helping to counteract the effects of the virus. It'll pass soon. Try to get some sleep."

"You'll be here?" She couldn't help herself.

His teeth glinted in the dim light. "I'll be here. I promise."

As Sarah drifted back into sleep the Doctor stood with his hands tucked into his trouser pockets, gazing down at her still face. Sarah Jane. His best friend.

She'd run by his side, when he'd been young and the universe full of possibility. She'd fought beside him – for him – with the fiery, indomitable spirit that burned within her like the stars of the brightest galaxy. Right from the start the connection he felt with her – this tiny, fierce, shining human – was so vital and deep as to be almost visceral. A new experience indeed for a cerebral Time Lord.

She had been the most marvelous of companions – steadfast, loyal, effervescent and enchanting. He didn't know how he had ever found the strength to leave her behind.

He thought back to the school, Deffrey Vale, and the terrible temptation that had been placed before him. "You can save them all. The Time Lords, reborn!" The very idea of it, of no longer being alone…the Krillitane had known just precisely how enticing the offer had been.

But once again Sarah had rescued him in the nick of time, as she had so often in their travels together – heedless this time not of her life but of her happiness.

She took his breath away. His Sarah Jane. Her words had given him the courage he needed.

"No. The universe has to move forward. Pain, and loss, they define us as much as happiness or love."

How well he knew that. How well, evidently, she knew it, too.

His earlier self hadn't surmised – hadn't paid attention to – how she had come to feel for him. That she had come to love him, not only as one friend loves another, but as a woman loves a man.

"I didn't realize," he whispered to her silently, and leaned down to press a soft kiss into her hair. "I'm so sorry."

"Whether it's a world, or a relationship, everything has its time, and everything ends."

Well, he thought determinedly to himself, this particular relationship wasn't going to end now. Not now. Not while he had breath in his body and two beating hearts in his chest.

Leaning forward slightly he pressed the tips of his fingers to her temples. Taking a deep breath to focus his mind, he reached out and projected his thoughts into hers, gently but firmly pushing aside the layers of fatigue clouding that bright, sparkling mind.

'Sarah,' he called. 'Stay with me. I need you.'

'Doctor?'

'I'm here. It's all right.'

'So cold…' Strange. She was hearing the Doctor, and he her, but she wasn't speaking aloud. Sarah roused a little, wondering.

'I know.'

The words, their deep sympathy and sincerity, reverberated in Sarah's brain. Then she realized – she wasn't hearing him with her ears, she was feeling him with her mind. At another time, on another day, and she would have marveled at his presence in her thoughts, at the touch of that soaring, mad, incandescent mind like a benediction. But she was so cold, and so, so tired… 'Doctor, I'm sorry.' Almost a ghost of a thought: 'I can't –'

'What do you mean? Course you can. You must!' His fierce, almost frantic, certainty coursed through her like a power surge through an electrical line. Then the urgency subsided a little, though not the conviction. 'I can't lose my very best friend. You can do this. Remember that time on Nerva Beacon? You'd crawled into that air duct and were certain you'd be stuck forever, but you managed to get out of it – with a little help from me, of course.'

'Help?' His words struck a spark in Sarah she didn't even know was there. 'You call that help – insulting me and calling me names?'

'Worked, didn't it?'

It had indeed, but she wasn't about to tell him that. But of course he was in her mind, and when she felt his mental laughter run through her like quicksilver she knew he'd read her thought anyway.

'My Sarah Jane, you of all people can do anything in this universe that you set your mind to. Think of all the places we've been – Karn, Skaro, San Martino, Peladon– all those people you've help save. Seem to recall you've saved me a time or two, as well – remember Professor Kettlewell's robot?'

'Oh yes. I do. And I saved you from the Wirryn,' she reminded him for good measure. 'And from Linx, and from that madman Harrison Chase's compost machine.' She stopped for a moment to allow her memories to coalesce, preparing to recite him the entire list.

'See what I mean?' Sarah felt his affection washed over her like sunlight, warming her from within, helping anchor her fast to the wondrous universe that they shared.

'And all those terrible monsters we faced. The Zygons, the Krynoid, the Sontarons, the Daleks – you and me together, we defeated them all. You must keep fighting, Sarah. You must.'

'Yes.' His thoughts revived her, but not as much as what lay beneath them. Not a thought, exactly, but an undercurrent of an emotion so unexpected and marvelous that she didn't even recognize it at first. Something so infinitely precious to her that when she did finally pinpoint its nature she wanted to reach out and capture it with both hands, and treasure it forever in her heart.

'Oh, Doctor.'

That feeling – that beautiful, indescribable feeling – was worth fighting her way back to him for.