A/N: This is part 3/5. Or maybe 3/6. The ending's gotten a little trickier than I was expecting. I'm new to this whole writing thing, so constructive crit is deeply appreciated. Thanks for reading!
When they reach the TARDIS, he turns. She's scrambling behind him, his shoes and jacket in her hands. She speaks to him between panted breaths. "Seems you're missing some things."
He can't answer her, can't look at her, but holds his hand out, palm upstretched. After a pause, she silently places his suit jacket in it. He accepts it and shrugs it onto his shoulders. Swinging his chucks by the laces, she tosses them towards his feet.
The wind has gotten strong on the hill, blowing her hair around her face and her skirt around her legs. He can't help but be reminded of the last time that he said goodbye. A windy day on another beach. Stinging tears well up in his eyes as he knots his shoes, but he holds his face still - it's dark enough she might not see.
"Doctor..." she starts.
"Rose," he interrupts her, his voice haggard. "Rose, please. I have to go." He tries to keep his tone light. "Tomorrow, okay? I'll see you tomorrow. Like we said."
"You won't."
"Rose, I told you..."
"You're not him, are you?" she says suddenly. She steps dangerously close, fire still dancing in eyes that see straight through him.
She doesn't seem threatened by this realization, just stating a fact.
After a beat of shock, reflexive babble streams from his lips in a torrent of noise and nonsense. Words burst forth that, looking back, he will never be able to remember or reproduce, but he hopes are distracting her enough to slip away.
Then he feels her warm hand parting his fingers. She squeezes firmly, quieting him, and repeats the question, so still and so close. "You're not him. Right?"
His body slumps, and he looks at her miserably. "No."
"You're a future him?" she confirms.
His eyes plead with her, but there is no refuge from her steadfastness. He can't prevent a small nod of assention.
Panic bubbles in him. "Rose, you can't tell him. You can never say..."
"Shh. I know. Reapers and stuff. Don't worry. I'll never breathe a word. Promise."
He nods again, relieved at her understanding.
"You should have just told me," she says flatly.
"You know I couldn't," he replies, finally feeling like himself. The walls have crumbled and now it's just him and Rose, no pretenses. In this zone of comfort and acceptance, he can't help but linger for a moment more.
"Yeah. I know," she affirms, smiling up at him, closer than ever.
He forces a grin at her, and squeezes her hand. "So, what gave me away?"
"I had my suspicions the first time around," she says. "But, this time I was sure."
Before he can make sense of that baffling retort, Rose is wrapped around him, fiercely claiming his lips with her own. He thrusts his arm between them, pushing her back and holding her at bay.
"We can't," he says breathlessly, "We... I can't do this. It makes things too hard. You have to stay. Preserve the timeline."
She furiously pushes off his arm. "Wake up, you git! I'm not that Rose."
"What?" he asks, brow furrowed and thoroughly confused.
"Doctor, look at me. Really look at me. I'm your Rose. Future Rose," she slows as she believes she sees understanding dawning on him. "You know... Defender-of-the Earth Rose?" she says hopefully.
The Doctor's posture straightens and she sees his legs flex under his trousers. His eyes narrow and the sonic screwdriver is suddenly out, its brilliant blue light casting harsh shadows on his face.
"Whoever you are," he levels, voice sharp with ice, "if you've hurt her, you're going to pay."
She can't roll her eyes large enough. "For the number of times you've bragged about the size of your brain, you can be incredibly daft sometimes. Right. Look here."
With efficient movements, she brushes her hair back to reveal a nasty scar along the top of her head. "Recognize this? I got it with you, fighting the Kurzons, right? But this one..." she parts her hair in the other direction, bowing her head down for his inspection. "New Year's Eve 2010. Firework startled an alien we were bringin' in, and he pushed me off the balcony. Fractured my skull, spent a month in hospital."
Seeing him unmoved, she frantically begins to dig in her pockets. "Papers. Here. Look," she places them in his bewildered hands. "Torchwood credentials. I'm a senior analyst now; got a huge staff working for me."
He plies his eyes away from her for a moment to glance at the papers. There's a photo ID of her. "Your hair is darker," he says in confusion.
"Yeah. Had to go blonde again tonight for the undercover job in case," she murmurs a bit embarassedly. "In case it wasn't you." She yanks the Torchwood papers away and replaces it with a photo.
"Remember the family? There's Mum and Pete. Just a few years older, but still together. And my brother, Steven. We tried to talk my mum out of the name, but there's no Aerosmith in the other universe, and she couldn't resist," Rose chuckles, glancing nervously at the Doctor.
She faces him full on, appearing strong and sure. "Doctor, it's me. I'm back."
He is at war with himself, not daring to breathe, his face sparked alternately with hope and grief. "You can't...it's impossible...You can't be here."
"You're impossible," she spits back at him desperately. "Doctor, can't you scan me or something? Oooh - check my DNA," she says, inspired.
"Useless," he responds rapidly. "Rose Tyler was already here. Plenty of creatures could have replicated her DNA by now." His words are harsh, but she thinks she hears a note of hope in his voice, like he might be opening himself up to the possibility.
Rose sighs, and kicks the ground a bit. "Where does that leave us then?"
"I'm not sure."
"What do you suggest? Is there anything that will convince you?"
He considers for a moment. "There is a way," he says. "But you won't like it."
"Do it."
"You don't even know what it is. You'd just..."
"...let you? Yeah."
They stare at each other for a moment, finding familiarity in the words. He takes a step forward, presses his fingers against her temples, and the Doctor is finally inside Rose Tyler's mind.