Rose looked around in slight puzzlement. She followed her mom and the Doctor in the blue suit as they exited the TARDIS talking amiably on the shore of Bad Wolf Bay. Suddenly it clicked and she turned to look at the Doctor in the brown suit and questioned, "Hold on, this is… the parallel universe, right?"
His face solemn and his hands buried in his pockets, he confirmed, "You're back home."
"And the walls of the world are closing again now that the reality bomb never happens," Donna added. "It's dimensional retroclosure." The Doctor in the blue suit smiled widely in recognition of her heightened intelligence; a result of the miraculous metacrisis the two of them had undergone. "See? I really get that stuff now."
"No, but– I spent all that time trying to find you, I'm not going back now!" Rose whinged.
"But you've got to." The Time Lord's voice was gentle but firm, leaving no doubt that nothing could be said to convince him otherwise. Walking toward her, he continued, "'Cause we saved the universe, but at a cost. And the cost is him." He stared pointedly at his duplicate, whose face fell in shock and he swayed slightly. "He destroyed the Daleks, he committed genocide… He's too dangerous to be left on his own."
The Meta-Crisis Doctor looked as though he had been slapped. "You made me!" he protested indignantly, unable to believe his ears; he felt utterly betrayed.
Donna's face was inscrutable, but her eyes were sad; the other's face was hard. "Exactly," he bit out. "You were born in battle. Full of blood and anger and revenge." When he spoke again it was softer. "Remind you of someone?" he asked, his gaze moving to Rose though he did not give her any time to answer. "That's me – when we first met – and you made me better. Now you can do the same for him."
"But he's not you," she pleaded, tears already starting to slide quietly down her cheeks.
"He needs you," he countered. "That's very me."
Donna shook her head; he was going about this the wrong way! "Bu-but it's better than that, though," Donna cut in. "Don't you see what he's trying to give you? Tell her, go on!" she urged the blue-suited Doctor.
He hesitated as Rose turned to him, taking a deep breath before he informed her, "I look like him and I think like him; same memories, same thoughts, same everything…" He held his breath a moment before continuing, as though scared to admit what he was going to say. "…Except I've only got one heart."
Rose blinked, unsure what that had to do with anything. "Which means?"
"I'm part human. Specifically the aging part; I'll grow old and never regenerate. I've only got one life, Rose Tyler. I could spend it with you. If you want."
Rose's jaw quivered. "You'll g-grow old at the same time as me?"
"Together," he confirmed.
She shook her head disbelievingly before slowly approaching him with her hand outstretched. He stood perfectly still as she did so, watching her face for a reaction as she pressed her hand against his chest.
As Donna and the other Doctor looked on with bittersweet smiles, the TARDIS gave a groan of protest.
"We've got to go; this reality's sealing itself off… forever," the Doctor in the brown suit said, retreating with Donna back toward their ship.
A tear slid down Rose's cheek as she ran after them with a shout of, "But! It's still not right." He turned halfway and looked at her more sternly than he had ever done before; this made her stutter, but she persisted in her argument. "'Cause… the Doctor's s-still you."
"And I'm him," he told her, nodding at the one still standing behind her; he hadn't moved.
"Alright, both of you answer me this…" Rose, frantically grasping at straws in what now seemed like a futile attempt to keep the Doctor (her Doctor; the proper Doctor) in her life, turned to the one behind her briefly before looking back at the original. The two identical Doctors came forward, each coming to a halt opposite his double in front of her; the one in brown at her right side and the one in blue to her left. "When I last stood on this beach – on the worst day of my life – what was the last thing you said to me?" Despite having addressed both of them, she didn't deign to turn her head to the left. When neither of them spoke right away, she desperately pleaded, "Go on! Say it!"
The Doctor in the brown suit swallowed. "I said, 'Rose Tyler.'"
Rose waited for him to continue but he didn't, so she pressed, "Yeah, and… how was that sentence gonna end?"
He stared at her for a few seconds. "Does it need saying?"
Rose's face crumpled then; this was not going at all the way she had hoped. She finally turned to the other one, scrutinizing him. "And you, 'Doctor'? …What was the end of that sentence?"
He silently steeled himself a moment before stepping forward and placing a hand on her arm. He bent close and whispered the words in her ear, then pulled back to see her face.
Her mouth dropped open. It was true. This was the man of her dreams. This was the man she had fought so hard and searched so long to return to. This was the man she had fallen in love with, and he just confirmed that he felt the same way. Overcome with emotion, she reached for the lapels of his suit coat to pull him in for a kiss, but he caught her hands before she could grasp them and leaned away from her. "I do love you, Rose Tyler. And that's why I'm leaving you here."
That's it for Chapter 1! Just a teaser to get you up to speed on where we're starting from here – near the end of the episode Journey's End, when the Doctor returns Rose and her mom to Pete's World after saving the multiverse from Davros and his reality bomb. I hope you enjoyed my embellished rendition of that scene up to the point where the storyline changes and, rather than sharing a passionate kiss, the Meta-Crisis Doctor forestalls Rose with an unexpected declaration: that this is goodbye.
This chapter is rated K as far as I'm concerned, but Chapter 2 will be deserving of this fic's T rating.