River Song lay on her side, naked on TARDIS-blue sheets, admiring her peacefully sleeping husband. He was beginning to realize - she hoped - that this was not the usual sort of infatuated admiration that a companion (or a friend, she smiled to herself) had for a powerful Time Lord. Theirs was a marriage of equals, and she loved it as much as she did him. She would let him sleep. The day had been very full, of loving and of pain, and the last bit had been a lot of both... for him especially.
The Doctor stirred, and stretched, and she smiled at him as his eyes fluttered open. "Hello, Sweetie," she murmured, and he returned her smile.
"Hello, my lovely bad girl River." He tapped her nose affectionately and their mutual smiles turned into something closer to goofy grins. This is going to be the best time, thought the Doctor, the time when we move almost in sync, and our timelines are closest together. He ran his hand down her torso suggestively... and ended the gesture by tickling her ribs, eliciting giggles and little shrieks of indignation. The tickles turned into caresses, and the shrieks into little moans of loving, a mutual pleasure in each other's bodies and minds and hearts and company, until they lay exhausted once again. "Mmm..." He stretched again, and flung one arm over River, hauling her in to lie spooned in his embrace, and they slept.
When River awoke again, she found herself facing him. His face was intent, and his hands finger-combed her hair gently, wrapping strands of it around his fingers and letting them spring back. She smiled drowsily at him. "So," she said sleepily, "You never did tell me about the most important Companion of all." And she was shocked to see how rapidly his face could change to a stunned mask of pain and grief.
How... How could she? he thought, riding a sudden wave of fury and pain, and in such a casual, teasing tone of voice, like it didn't matter, like it hadn't nearly destroyed me! "I don't want to talk about Donna!" he all but shouted at her, and he was up and out of the bed faster than she could react, stumbling to the bedroom door and trying to wrest it open.
It wouldn't budge.
Oh no, thought River frantically, what have I done? She practically leapt out of the bed after him and didn't stop to put on a robe. She threw her arms around him as he struggled with the door, too distressed to find his screwdriver, tears running down his face. "Oh, my love," she whispered urgently in his ear, "I didn't mean Donna Noble, please, please listen to me, please, Sweetie, you know I wouldn't hurt you like that, not deliberately, please!" There were tears on her face now too; she pulled him away from the stubborn door and they tumbled to the floor. He curled up there, shaking, hands over his face, and she put her arms around him again and murmured soothing nonsense into his ear until he stopped shuddering with remembered guilt and pain.
Eventually the Doctor sat up, scrubbed the tears off his face with his hands, and - without looking at River - half-whispered, "I'm sorry. I... I thought..." He began to wave his hands around in that helpless way, the way he had when he was at a loss for words, and she caught one of this hands and brought it to her lips.
"It's all right," she murmured against his fingers, "You thought I was teasing you, making fun of... well... what amounts to the death of the only sister you ever had. Hysterical ranting was not uncalled-for." She smiled at him. "I didn't mean to hurt you. I know what... what you had to do to keep Donna alive, and I-" She broke off as he kissed her, trying to show her that he knew she hadn't intended to bring all that up from his past. He realised - now - that she wouldn't do something like that; if she felt the need to bring up his past mistakes, she would only use those mistakes where he had hurt her, not those of the countless friends he had had before they met. But he hadn't trusted her, again, and he was terribly afraid he had hurt her. Again. So he needed to show her, he needed her to understand that he hadn't meant it, he'd misunderstood, and so...
And so he kissed her.
And she kissed him.
And everything was all right again.
He let out a sigh of relief. "River? I don't mean to pry, especially after all that, but, well... oh never mind, it's not important, rubbish question-"
"Oh, shut up," River interrupted, smiling. "You know I'll tell you as long as there aren't spoilers."
"Er... well, if you weren't talking about Donna, and we've already touched on Rose and Susan and Sarah Jane and the rest... then who did you mean by 'the most important Companion of all?'" He looked uncomfortable. "I mean, you're not exactly modest, but I don't think you were talking about yourself, and you're certainly the most important now, and well... who did you mean?"
She laughed. "Work it out, my love. Who's been with you all along? Who's basically your wife and your mother? Who do you go to when your other friends aren't available?"
He stared at her. "But... but you already know all about her."
She laughed again, shaking her head. "Go on, my love, tell me how you feel about her, your Sexy Old Girl. I love her too, but I want to know her history. Her history with you."
So he did. He told his wife about his other wife, the one person who understood the timey-wimeyness of his universe better than he himself did, who had been with him for hundreds of years, who had known him through all the other traveling companions, from Susan to River.
Who had loved him and cared for him and taken him where he was needed.
Right now that place was here, with them, his new wife and his longtime companion.
And River was happy, together with her madman and his box. And the Doctor was happy, together with his loves. And the TARDIS was happy, with her beautiful thief and the child of her heart. And together the three of them traveled the universe; a woman, and a madman, and their box.