One day, River mapped the TARDIS interior out of curiosity. When the Doctor asked her hours later where she'd been, she gave him the mysterious smile she knew he hated, added milk to her tea, and refused to say. Besides, she wasn't finished yet.
"I was occupied."
Rather than argue with him, River took a long drink. She set the cup aside, smiled again, and made him forget every inquiry he'd ever made that wasn't, "Would you do that bit again?"
She hid the map in her own room. Although she far preferred the nights she spent in his, River never knew for certain from visit to visit if the Doctor she would meet had had her in his bed. She kept her diary, and she kept her notes, and she treasured the increasingly rare visits from the Doctor late enough in his timeline to know what she meant to him.
"Let's go to the Singing Towers of Darillium," she said one day over the remains of breakfast. The Doctor with her was on the young side, skittish and pliable and unfortunately not ready for marital bliss. He also lacked his later self's ability to hide emotions on this face.
"Boring." He swept the crumbs away and leapt to his feet. "We'll take a trip somewhere more interesting. Praetor Core. They have the most amazing sea turtles. Huge! You can ride them! Riding on sea turtles, can you picture it?"
"I know," River said. "You ought to take Amy there some day."
He leaned close. "Is that a spoiler?"
"Just a suggestion. I think she'd enjoy the trip."
Amy and Rory had disembarked for a while. Back to Earth, back to sanity. They'd be home in the TARDIS soon enough. "Perhaps I will."
Instead of going to visit the giant sea turtles, the Doctor curled up with a favourite book, and River resumed her map-making. She was an archaeologist by training and by joy. Discovering new places and carefully noting her findings thrilled her as much as any starlit chase. The TARDIS had so much to share, opening her doors before River could even ask.
River wondered at the spaces within spaces. The TARDIS contained infinity, and also a great deal of junk. Her love never could discard anything he once cared about, and he cared about so much and so very many. She found bedrooms, kept in stasis as clean or jumbled as their owners left them. She found storage rooms with artefacts some museums would have traded anything for, and some artefacts she suspected had been stolen from same.
She found the books.
Over dinner, River asked, "When were you planning to show me the Library?"
The Doctor held his plate of grilled lamb with vegetables, a meal the TARDIS had provided fully-cooked from some unknown site. He stared at River, food forgotten, face losing colour. "What?"
"The library. It's enormous. You've even got The Secret History of the Time War in there."
He glared. "You didn't read it, did you?"
She took a sip of champagne. "Me?"
River had only taken a quick glance. She'd marked down the location for a longer perusal later.
"Are you exploring the TARDIS?"
"Of course. She's a beauty. She likes me, you know."
He cast his eyes to the closest bulkhead. "I know." He looked down at his food, and set the place aside. "Let's go somewhere. You and me. We can visit the Horsehead Nebula back when it was still a colt." His grin was infectious. "Or we could go snorkelling on Hyneria. The Dominar owes me a favour."
"What about Darillium?" She spent her time reading his face, and got her answers.
"Dull. I told you."
She didn't press the issue again.
The next Doctor to pick her up wore an entirely new face, which wrinkled with surprise and delight when he saw her. She didn't have time to explore his TARDIS.
After that, she met up with the version she most preferred, with his bow tie and old man's mannerisms. He addressed her as his wife, and treated her as his lover. Preening with the attention, River ignored her maps. Not long after, she got a letter in a blue envelope, and she watched herself kill her love. That Doctor was followed on by a younger version hours later. River ticked off places in her diary, keeping watch over her parents as best she could.
When time allowed, she went through the corridors of the ship. Even when the Doctor didn't know her, the TARDIS did, keeping River's bedroom as she preferred, with the growing map in the same hiding place. She'd added more sheets of paper, attempting the impossible: capture multiple dimensions of layered space. The project kept her spirits up when Amy and Rory were nowhere to be found, or on visits when her bed was cold and lonely.
She asked about the Towers. She spoke about the Library. Younger Doctors changed the subject. Older Doctors merely looked away.
Something was coming. She didn't have to wonder how he would accept her death. With their timelines all askew, she knew her life with him was little more than his long mourning period as he sat up with the dead. When she was gone for him, truly gone, would he come into her room, see her things, find her map? Had he done so already?
Their timelines overlapped again when her parents died. She hadn't known how she'd lose them, how he would. She found she couldn't face walking out the door not knowing if the Doctor she met next would remember today, would know they were gone. Her own grief coloured her voice and her eyes too much to hide from him.
She tossed off her poor joke about psychopaths, then left him alone in the Control Room while she went to the kitchen for tea. Around her, the TARDIS hummed sadly.
"He loses everyone," River said to her as she filled the kettle.
The TARDIS reminded River the Doctor wasn't the only person who lost everyone. River sat in her chair and sobbed. She could write her book tomorrow.
When she woke the following morning in his bed, she donned a dressing gown and crept back to her own room. Her clothes hung in the wardrobe. Her hairbrush lay on the washing stand. Her map lay hidden under her bed. He would find her things and his hearts would break all over again. She would have to take away her personal items. She would burn the map.
She turned. He stood in the doorway, his own dressing gown tightly-cinched at his waist, his hair wild.
"Sweetie. I thought you were asleep."
"You were gone." His face was so lost. She dropped her papers and went into his arms.
"I'm here." She turned, seizing her brush. "I wanted to fix my hair."
His eyes easily picked out the papers on the floor. "You made a map?"
"Oh. That. It's nothing."
He grabbed a sheet before she could stop him. "This is a map of the TARDIS."
There remained no point in deceit. "Yes."
"That you made."
Annoyance poked through her confession. "Are you sleepwalking? Should I worry about waking you and risk your legs falling off?"
The Doctor sat on her bed, fetching more papers. "This is...."
"I'm sorry," she said, hoping to stave off the rest, and hoping more she could snatch the map away and push him down to the bed properly.
He looked up at her. "It's amazing. You really did all this?"
"Can I have these?"
She hadn't expected that. "Why? It's your TARDIS."
"Yes, but," he looked down at her drawings and notes, "this is wonderful. I've never mapped her before. She doesn't tend to keep the same shape long."
"She knows you bore easily." River folded her arms.
"Never of her," he said, and reverentially tidied the papers. He smiled at River. "My girl is endlessly fascinating, inside and out, and I will care for her forever."
Oh. He was talking about feelings again. He was rubbish with feelings. She was rubbish with feelings. River sat down beside him and took his hand. "Sweetie, don't."
But his grin had come back, and if it was duller than it had been a day ago, she didn't blame him at all. "Let's go somewhere."
River sighed. That was always his solution. Feeling bad? Set a course for some place and time that could distract him from his self-loathing. "I really don't..."
The Doctor brandished the papers in his hand. "I was thinking we could go to the games room. I haven't been able to locate that for two hundred years." He pointed to a spot on the map she'd barely explored. Games had seemed ever so dull when she had all of time and space to play with.
She never could resist that smile, though.
"Let me get dressed first."
His eyes dropped. He set the map carefully aside on the floor. The smile stayed. River found one of her own to match. She ought to make a naughty comment about giving him something else to explore, or joke saucily about getting dressed later.
He kissed her before she could decide which to choose, which was, she decided, for the best.