There was one room in the TARDIS that the Doctor always kept locked. That was the one room that no one but he was allowed to enter. It was an important room; a special room; a room that brought him as much sadness as it did happiness; possibly more in the sadness department.
It was a room filled with memories of warmth and laughter, embraces and whispered goodnights, smiles and kisses on the cheek, and the smell of toast and tea in the morning. It was also a room filled with memories, some repeated once in a while, of shed tears, regret, longing and loneliness. It was a complicated room, so the Doctor kept it locked. He didn't want just anyone wandering in there and changing it. Not after he'd gone to all the trouble to keep it exactly as it is.
It wasn't until after his regeneration that the Doctor briefly forgot about the room. He'd had so much more on his mind than usual, what with Amy Pond and cracks and Daleks and the end of time itself. He'd had so much on his mind after his regeneration that he never even checked to see if, after repairing itself, the TARDIS had left that one room locked.
It hadn't. It took surprisingly longer than expected, but the Doctor's Ponds stumbled across that one special room on a particular evening while looking for a secluded place to snog. What they found, however, made them pause.
It was a room unlike so many of the others in the TARDIS, and the first thing that hit them was the smell. A scent so perfectly preserved that whoever had left it behind could have been in there no more than a few hours ago, which was impossible given they were the only two, other than the Doctor, on the time ship. They were standing in a bedroom, a bedroom that appeared to have belonged to a girl, given that there were clothes and earrings scattered here and there; a union jack shirt draped over a chair, a pink sweater balled up on the bed near one of the pillows. It was so messy. The Doctor never left any of the rooms on the TARDIS in such disarray.
Amy had been about to turn around and stalk with purpose to the control room to confront the raggedy man about the peculiar room, but when she and Rory turned he was standing there right behind them, looking pale and somewhat pained. Before they could get a word out, he scrambled forward and shut the door, pulling out the sonic and choosing a specific, memorized setting before locking the door; a setting that would keep everything just as it was so painfully long ago.
"What was all that?"
Amy was the first to speak, and the Doctor remained quiet for a long, long moment. Rory was about to pull his wife back down the hall to give the Time Lord some space when he finally spoke up.
"It was her room," he murmured, and Amy frowned, her brow furrowing. The Doctor had never mentioned a 'her' before.
"Who's room? What 'her'? Who?"
Again, the Doctor was silent. It took him a while, but he slowly turned to face them both, leaning against the door with something like defeat. He looked so tired and, for once, so very, very old. Haunted, even.
"Rose."
After a bit more prompting, he launched into a description of Rose Tyler; his brilliant pink and yellow human, who he'd cared for so deeply, more than she'd ever know, but who he'd lost, first to another dimension and then, somewhat intentionally, to a copy of himself. He spoke of her with a mixture of fondness and heartache, and ended by peering at the handle of the door, stroking it as though it were something precious; to him, it probably was. One of the last things on the ship she had touched; of course it was precious.
"After all this time?" Rory asked, causing the Doctor to look back to them, and the Doctor knew what he meant. Years after losing her, he still kept her room just as she left it, using a specific setting on the screwdriver to seal it off in a way that would keep her scent in there, too. Swallowing the lump in his throat, the Doctor clutched the doorknob a bit more tightly, his voice quiet yet dripping with heartfelt honesty.
"Always."