Author's Notes: Written for hihoplastic in the River/Doctor ficathon on spoiler_song. The prompt: "There's a fine line between what can be, what will be, and what must be - and River knows that better than anyone."
He couldn't die here. He couldn't. She could see the paradox without even thinking about it. If the Doctor died in the Library, then he never met Amy Pond. Amy Pond never traveled in the TARDIS. Melody Pond was never born (or if she was, it wasn't at Demon's Run). River Song would never exist. No one called the Doctor to the Library, and yet the Library was where the Doctor died. Oh, time might find a way to repair itself over the damage of his death, but River couldn't be sure, and she didn't want to risk never having lived at all.
So this is the end, she thought as she pulled out the handcuffs and locked him to one of the computer terminals. And you always knew about it, you… She wanted to hate him for knowing. Every moment they had shared together, every day, every hour across the whole of time and space he had known that she was coming to this. And he'd never hinted at it, never in all those days… but why would he? Spoilers were spoilers, they both knew that.
She dug his screwdriver out of his jacket and tossed it out of reaching distance. He'd probably be coming around in a few minutes and she knew the first thing he'd try to do was save her, but she couldn't let him do that. She couldn't even tell him why. She couldn't tell him that she wasn't just saving his life and the lives of all those people, but her own life as well.
Part of her wanted to hate him for always knowing. It was almost easier to, with this face. She had only seen him like this a bare handful of times, and he'd always been so tense around her, holding her at arm's length, it seemed like. Now she knew why. And she understood as well as he probably did—her Doctor, wherever he was now—why this had to happen. He couldn't die here. He didn't die here. Yes, time could be rewritten, but not all of it. Not the fixed points—not Silencio, not Trenzalore.
He couldn't die here, and so she wouldn't let him. She didn't want to risk having never been born, and, selfishly, she didn't want to risk having never met him. To risk rewriting her past and forgetting all those beautiful nights she'd shared with him. Like that last night, just a few days before.
She had been grading assignments when he knocked on her front door, beating an irregular rhythm that gave him away at once. She smiled and set the papers aside, getting up so she could open the door to let him in.
"Hello, sweetie," she said as she opened the door.
He smiled. "Hello, dear. Are you busy?"
"Are you?" she asked, looking him up and down. He was wearing that marvelous tuxedo she'd seen him in at Amy and Rory's wedding, and in Berlin all those years ago. It looked as though he had finally trimmed his fringe from the last time she'd seen him as well. "You look like you're going somewhere special. Am I invited?"
"You're always invited, River. Are you busy?"
"Sweetie, am I ever busy when it comes to you?" He just smiled at her, and she kissed him swiftly on the lips as she stepped out on the porch, closing the door behind her. She took his offered arm and together they walked down the front steps to where he'd parked the TARDIS in the garden.
"May I ask where you're taking me?" she said as they took off, the TARDIS engines groaning loudly around them. "Or is it a surprise?"
"It's sort of a surprise," he replied. "Why don't you go change, and I'll explain it to you before we get there."
"All right, love." She pulled him away from the console to give him another, lingering kiss, then sauntered off down the stairs towards the wardrobe.
The surprise was the best one she could have imagined: the Singing Towers of Darillium. She'd been asking him for ages to take her, and had considered going by herself a dozen times over, but it seemed that that would have spoiled it. And she was so glad she had waited now.
The Towers sang a song that lit up the night. She and the Doctor were just two people out of hundreds there, but River felt as though they had this night all to themselves. She leaned into him, her head on his shoulder and her arm around his waist, her eyes warm with tears as she watched the Towers' light.
The song was nearly over when she realized he was crying, too. She looked up at him. "Love? What's wrong?"
"Nothing," he replied too quickly, his voice thick.
"Nothing you have to worry about," he said, but the tears on his cheeks made her feel otherwise.
She turned to face him as the Towers' song faded away, cupped his face in her hands and gently wiped away the tears. "Doctor, what's wrong? What's the matter?"
He did a better job of collecting himself that time, managing a smile as he reached up and took her hands in his. "It's not important right now." He kissed her knuckles. "I love you, River."
"I love you, too, Doctor. Are you—are you sure you're all right?" He was still crying, for all that he was smiling at her, tears flowing down his cheeks at almost regular intervals. "Is there anything I can do?"
"You're already doing it, River," he said. "You're here." He dropped her hands then, reaching up to cup her face and pull her into a kiss.
He kissed her with a slow, fervent passion, his tongue pushing past into her mouth, his teeth occasionally catching on her lips. She returned his affections in equal measure, her hands clutching at the lapels of his jacket, pulling him closer until it seemed there was no space between them at all. His fingers twisted and tangled in her curls, and she moaned softly and pulled him even closer, kissing him even more fiercely.
They only separated when River began pulling at his bow tie, and even then it was a slow thing, the kiss turning into lingering pecks with every ounce of passion still behind them. They walked back to the TARDIS with their arms entwined, pausing now and again for another kiss.
The Doctor held her hand so tightly it hurt.
They began again almost as soon as the TARDIS doors shut behind them, kissing each other and shedding clothing in increments as they made their way to the bedroom, where they fell into each other's arms to make love at last.
He whispered "I love you" with each kiss and caress, and she whispered it back to him and wiped away his tears, for he still was crying and she wished desperately that he would tell her what was the matter.
Hours later, they lay next to each other, his arm around her shoulders as she rested her head against his chest, listening to the steady rhythm of his hearts beating.
"I love you so much," he whispered.
River smiled. "I know, sweetie."
"I always have, even—even ages ago, when we didn't—when I didn't know you that well."
Her smiled widened, and she shifted so she could look at him properly. "Oh really?"
He was smiling. "You've always been interesting, River, and you'll never stop."
"Well, I certainly hope not." She leaned over and kissed him.
He dropped her off several hours later, but not without giving her a gift: a sonic screwdriver, rather like the one he owned. "This might come in handy. Thank you, sweetie," she said, kissing him again.
"I thought it might." He smiled, but she could tell it was a strain for him.
"Sweetie… Doctor. Are you sure you can't tell me what's wrong?"
He shook his head. "No, River. I'm sorry, I am, it's just—"
"No, no, it's all right. I've got an expedition coming up in a few days," she said brightly, hoping the change of subject might help somehow. "You're welcome to join us if you'd like."
"Drop me a line," he said, tapping his jacket. "I'll be there."
"Thank you, sweetie."
"Of course. I love you, River."
"And I love you, Doctor."
They kissed one last time, and she watched from the door as he left, the TARDIS vanishing in a whirl of wind and light.
She never for a moment suspected that it would be the last time she saw him, that the Doctor she met at the Library wouldn't know so much as her name. That he would look at her like she was a stranger. That everything she had feared about his first meeting with her would come true.
And she had never guessed that she would be coming to the Library to die.
But that was the way it was, she thought as she worked, fusing wires together with her screwdriver to get the computer core ready for the energy transfer. This was the way things had happened, the way they would always happen. There wasn't another way out. Time could be rewritten, but not all of it. Not today.
There were still a few minutes left when she finished. There were a handful of small things left to do, but she would save those for the last seconds of the countdown.
The Doctor was still unconscious. She knelt by him and gently touched his face again, hoping that she wouldn't wake him. He looked so different, but she couldn't help but love him still. He wasn't her Doctor, not yet, but he would be. He would get there eventually, through every day across the universe they spent together. It would never end.
"I'm sorry, my love," she whispered, and she kissed him briefly on the lips, her touch so light it might well have been nothing at all. "I love you."