"Time can be rewritten! / Don't you dare! Not those times..." ~ Doctor Who, "Forest of the Dead."

Ever since New York, when River had told him that she had been pardoned, The Doctor knew his time with her was coming to an end. He had made many memories with her, more than he had hoped for when he first dropped her off in prison. The times spent just with her were very special to him, times when the Ponds were home being "normal." Later, he wasn't sure how he would have coped if River had not been there for him after Amy left. And now he was about to lose River, too. It was more than he thought he could bear.

When he had showed up at River's doorstep, he had been resolved to take her on one last spectacular trip. One more time, he would get to hold her and feel her and show her his love. He knew her time was coming, and he had asked her where she was going merely to confirm his fears. The Doctor had told himself that he could act like nothing was wrong. But realization sank in as soon as he had seen her smiling face. This would be the last time he whisked her away. The. last. time. And River would find out that he had known all along how things would end.

He checked the console absentmindedly while she slept in a room nearby. I could stop her from going, he thought. We could travel through time and space together for many years more. Just do it. Just take her somewhere other than Darillium, anywhere, and somewhere else after that, and on and on until she forgets about that library. But he knew that was not in his power. River would get suspicious if he tried to change her plans - she already thought he was acting strangely. And he had seen her fate; it was now a fixed point in time. The last time they had tried altering a fixed point - when River had tried not to kill him - the entire universe had almost ceased to exist. But then we got married. They had fixed the universe and cheated death and got married. Surely we could do it again! There must be a way! He pounded the console of the TARDIS in frustration at his own powerlessness.

"Rose… Martha… Donna… Amy… Rory… River." Speaking these names aloud, he felt like he could never love another companion as much as he had loved the ones he had already lost. "Oh wake up, Doctor! You chose this. You always choose this. You pick up companions along the way like they were stray puppies, and you name them and love them and when they die or run away you howl and scream because you have to go on living without them! I will not go through this AGAIN!" His last word reverberated around the control room of the TARDIS and came back to him sounding distant, as if it had taken years to come back, not seconds. Afraid of waking River, he stormed down to the underside of the console, feeling like breaking something.

"Why can't I save her?" He was still tempted to turn and run, River on the TARDIS next to him, where she belonged. He didn't care about the fixed point or the end of the universe, anymore. He used to care, but now he couldn't. He could not imagine going on anymore, without his loved ones beside him.

If he kept her from going to the library, it was very likely that he would die there, along with Donna. Then he never would have met River. Maybe that was best. River would cease to exist, actually, since she had been conceived on the TARDIS itself, and he would be dead. But he wouldn't have to feel the pain he was feeling now. If he had died, he wouldn't even have to mourn Amy and Rory. But then he never could have saved Amy from the crack in her wall. (Would the crack even be there if it weren't for me?)

But an echo came back to him through the fog of despair that was threatening to engulf him. "Don't you dare!" River had been adamant about not rewriting the times they had spent together. She would rather die there in that library saving him than to never have met him. It's what she wanted. She had made her choice already, and she would make the choice again. No, he could not deny her final request to him. He would not.