Understanding Is Impossible

River sat with her back against one of the walls of the TARDIS consul room, staring into the distance distractedly. She fiddled with the buckle on her vortex manipulator, the way she always did when she was nervous. She wondered why the Doctor hadn't disabled it in the way he did to its previous owner, no other than Captain Jack Harkness. She knew little of the man, being one of the few people she had never managed to meet, other than that he had been a companion to the Doctor's ninth and tenth selves, and the fact that he was American, gay and had the same birthday as her. (A/N: John Barrowman and Alex Kingston have the same birthday, so I thought it would be fitting if Jack and River did too)

The Doctor stuck his head around the monitor, indifferent curiosity sparking in his eyes. His eyes were strangely beautiful to her, the hazel-green encapsulating hundreds of years of space, time and near misses. There she also saw his age, all the great events of historical importance over the years, and all the things he hid from her and his companions.

"You right, River? You look as if the world has just ended or something."

Her response was more curt than she had expected, and wanted it to be.

"Well, there are millions of planets out there that you need to save, apparently, because we can't let time play out by itself, it always needs you to save it but anyway, that doesn't matter, because you can just wander around the TARDIS all day and show your companions faraway lands, but that's quite alright according to you!"

The Doctor's shock registered within seconds, and a hurt expression came over him. He reached for his bow tie absent-mindedly, fiddling with it in confusion. He did not know River like this, seemingly angry for no reason. She seemed almost confused about him, as if she didn't know anything about him, as he didn't know about her. But he knew this wasn't true. His past was her future. She knew him better than anyone did, and what was going to happen to them. So why was she so angry? Had he done something wrong? He hated upsetting River, it hurt him more than anything, and in a strange way, he was scared of her. Had he missed something? Or more importantly, what was she keeping from him?

River realised she had been staring at the Doctor for just a moment longer than she should have been. She hated hurting him, as he clearly hated upsetting her, and after all, she did and always would, love him. He was, technically speaking, her husband, even if she wasn't his wife. Yet. She glanced up at him again, revelling in the perfect silence, even if most people would have called it awkward. He had somehow managed to neaten up his hair with some hair gel from dread-to-think where in the TARDIS. It occurred to her that she probably shouldn't notice these things, but what did that matter? She loved him, she was married to him, and she couldn't breathe a word of it to him.

Unwillingly, Professor River Song found herself crying.

The Doctor quite clearly hesitated a moment before asking what was wrong. He really did not understand humans sometimes, they were so… Alien.

"River? River are you okay? What's wrong?"

River Song had never been particularly nice. Fine, she was capable of comforting others, helping defeat aliens and falling in love, but 'niceness' wasn't her strong point. So when the man she loved who didn't know she loved him, who she worried didn't love her asked if she was okay, her first instinct was to retaliate.

"You just don't understand do you? You think the universe always needs you to save it, but you never give up any of your hundreds of years, that will most likely turn into thousands of years with your many faces. So many people love you, Doctor, and you don't give up one second for them. Your companions risk their lives for you; go along with your non-existent plans, and what do you give them? Another chance to risk their lives. Amy loves you. Martha loved you. Donna…"

She trailed off, realising that probably wasn't the best example, but then continued her rant.

"Jack loved you. Rose…"

River's sobs racked her body as she struggled to get the last words out.

"Loved you."

River stood up, hesitant steps leading her into the Doctor's outstretched arms. She buried her head in his chest, sobbing into his shirt while inhaling thousands of years and thousands of galaxies. He ran his hand through her hair, a sad look coming over him. His touch sent a thrill through her body, and, even though it was not the first time for her, it was for him. His firsts were her lasts. Tears streaked down her face anew at this realisation.

The Doctor was confused, to say the least. He had always thought of River as strong, a light when darkness consumes all. Now… Now he didn't know. He had to make her understand.

"River Song. You have to know I have no idea what happens in the future, and I am just beginning to find out who you are. Rose, Rose was different. I will not deny I didn't love her. But not me. Not this version of me. You know she's stuck in a parallel universe, and, if she wasn't, well, maybe it would be different. But she is, and she has a version of me. My other companions, they all love me. And I love them, as friends. I take them places to tell them that, to show them how much they mean to me. The universe is a big place, River, and I am a lonely man. I don't mean to get into the messes we usually do, they just happen. The TARDIS makes it happen, instead of taking me where I want to go. She wants me to help the world, wants me to be a doctor. But River, oh River. I love you sweetie."

The Doctor moved and lightly kissed River's forehead sending electricity sparking through her body. She loved the feeling of his touch, it made her come alive. She would tell him; she had to tell him. It was impossible to keep from this amazing man that she was married to him. Time would crumble, the rules thrown aside. But she would have what she had wanted for all these years: him. She would have the Doctor. Not just as a fellow time traveller who brightened up her every day, but hers.

"Doctor, I will tell you everything. Or as much as I can without ruining the space-time continuum. Tell me something. How many times has the world ended?"

"None?" The Doctor answered, almost unsure of the answer himself.

"None," River clarified. "Do you know why that is? Because you are always there to save the day, just in time. How can you not admire someone for that? Every time there is even the slightest disturbance, you swoop in with the TARDIS and right every wrong with a mention of your name. Not a single death caused. Most of the time."

She hated adding that final comment, because she knew how hard the Doctor tried to prevent deaths, but the world didn't always let that happen. Every death was written on his face, a kind of guilt that could not be erased. With the Timelords dead, he had made an oath to heal the world. But fate would not allow that. The world wasn't perfect.

"So while you're busy saving the world, I have to rely on weapons of a different universe and of a different time, and I have found mercy is no longer possible. Just another word that was outlawed by the rules of the cosmos. You saw what I did to that dalek. But I was never content with that. I will never be content with that. You made me a better person, Doctor. And I never can repay you for that, a gift that will never be forgotten, as it made me who I am. But I am not me without you. You're my Doctor."

The Doctor's smile became a goofy grin that rivalled that of his ninth self. He was married to River Song.

"Perfection is possible," he murmured, half to himself and half to River.

It was River's turn to smile sadly. "No, you are possible." She began to fiddle with her vortex manipulator, typing in the activation code. "Until next time, Doctor. I had better go and make sure I didn't just destroy the universe."

"How are you going to do that?" the Doctor questioned, his joy turning to sadness at her going.

"I'm going to visit one of your old friends."

"Who?"

"Captain Jack Harkness." With that, she activated the vortex manipulator and vanished into the depths of space and time, leaving the Doctor standing in deadly silence, yet again alone. He turned back to the monitor, expecting it to be on the same screen as earlier. Instead, it flashed with a message.

LATER, SWEETIE.

The Doctor smiled. He would journey onwards and would meet River again soon enough. Taking his mind off the subjects it was determined to stay on, the Doctor began running around the consul, flicking numerous switches and buttons.

"Next stop, Earth, 1790! Geronimo!"

The TARDIS fell through time and space, ready for yet another adventure.