It had been nearly a hundred years since he left her. A hundred years since he got back onto the TARDIS with Donna and faded away, leaving the woman he loved with a copy of himself.
There had been several Companions since - even ones he might have had feelings for. But he never really forgot her.
He knew that there was one night a century when the stars aligned and the planets were ordered just perfectly to allow a quick trip through the Vortex to her world. And if he planned it right, he could make sure to get back after some time had passed, so that he could avoid bringing too much heartache to her.
The night came, and he dropped his Companion - a sweet, but deliciously snarky twenty-something named Alfie - off at his home. He told Alfie he had a "quick, personal thing" to do, and that he'd explain when he got back.
When he was alone, he set the coordinates. "Come on, Sexy," he murmured to the TARDIS. "I know it's not easy, but I need to know she's okay."
With only the most minor of turbulence, she managed to land him just down the road from a small house in Greenwich. The Doctor checked the Universal Clock on the console - January 13, 2017. That was roughly 2011 in normal Earth time, so…
Five years.
He hoped, in his hearts, that five years was long enough.
After he rang the bell, he nervously straightened his bowtie and smoothed his hair. Rose wouldn't recognize him. He'd have to explain that he regenerated again… He'd definitely leave out the fact that he'd been alone when it happened.
The door swung open and The Doctor found himself staring at…himself.
The Metacrisis Doctor had aged, and it was weird to see himself with greying hair and wrinkles. But then he noticed the smile.
"It's you," he said softly.
The Doctor nodded. "I…had the chance to see you. Both of you. I couldn't pass it up."
"No, you couldn't." His other self held the door open a little wider. "Come in."
"I can't stay. I only have a…"
"You have enough time to see Rose. And Amelia."
Amelia. The Doctor stopped in his tracks. "A-Amelia?"
The Other Doctor grinned. "My - our - daughter."
Coincidence. It has to be, he thought. Perfectly common name in Britain. He should have listened to his own advice: never ignore a coincidence.
When he got to the seating room, Rose was sitting on the couch, her head down as she read aloud from one of the Harry Potter books. Curled up at her side was an incredibly familiar looking ginger girl.
The Doctor's hearts started beating double-time.
In this Universe, his Rose was the mother of his Pond.
"Rose, Amelia, we have a guest," The Metacrisis Doctor said gently.
Rose's honey-coloured eyes met his first, and she gasped slightly. The Doctor wondered briefly how both his other self and Rose recognised him, but quickly realised that the telepathic link that he'd believed dormant must have still connected them – or, at least, the two Doctors – somehow.
"Doctor," she breathed. "Why... No, how are you here?"
He started to explain, but little Amelia, four years old and already with the same fire in her eyes as his Amy had ever been, spoke up. "Mummy, who's that?"
The Other Doctor, (I really must find out if he has a name, The Doctor thought,) stepped over and hoisted Amelia onto his shoulder. "Amelia, this is a very old friend of your mum's. We call him 'Doctor'."
She smiled, holding out a tiny, polite hand. "Hello, Doctor. I'm Amelia Jessica Smith."
Ah, so he stuck with John Smith, The Doctor realised. "Hello, Amelia," he replied, shaking her hand. "And how old are you?"
"I'm three!" she replied proudly. "But Daddy says I act more like I'm ten."
The two Doctors shared a look – clearly, little Amelia had inherited more than her father's politeness. "She's just very advanced for her age," John said, the unspoken meaning behind it understood. Amelia was fully human – there was no Time Lord biology in Rose's little girl.
"Amelia," Rose spoke up, and The Doctor's head spun at the sound of her voice. "Can you take Daddy upstairs and feed your hamsters, please? I need to talk to The Doctor."
"Okay, Mummy." John smiled at his wife and disappeared up the stairs, holding Amelia up like a giggling, flailing airplane.
They were out of sight before Rose stepped up to The Doctor. "You never answered me."
"You asked me something?"
"Yes," she replied, and he saw the hint of a smile when her tongue touched the back of her teeth. "How are you here? I thought we'd never see you again."
He sighed. "It's been a hundred years for me, Rose. Once in a century, there's a chance to visit parallel worlds...if you know how. I couldn't miss the chance to make sure you were okay."
Her eyes were sad as she reached up and straightened his bowtie. "A hundred years," she echoed. "God, it's only been five for me."
"The life of a time traveller," he quipped.
Another almost-smile. "How many regenerations?"
"Just one, so far. A couple of false starts..."
"Please tell me there aren't any other Metacrises out there."
"No, no, of course not, there's just..." He stopped when he saw the genuine grin on Rose's face. "You're mocking me, Rose Tyler."
"That's Rose Smith," she replied. "And yes, I am."
"Change your name all you like. You'll always be Rose Tyler to me."
Her face softened again. "Well, now that you know I'm happy, I suppose you'll be leaving."
"I have to. I don't have too much longer before the walls close again." He touched her cheek. "But you are happy?"
"Very. I need to thank you for what you did." She swallowed thickly. "He's wonderful – just like you always were."
The Doctor smiled warmly. "All because of you." He stopped, hesitant to say the next part. "You know, Rose... Your Amelia... I had a Companion once. Her name was Amelia as well – well, we called her 'Amy'. I called her 'Pond'. But anyway, getting off topic. I think your Amelia and mine are...parallels."
"Wouldn't surprise me," Rose said evenly, though her lip trembled. "We always did manage to find each other somehow." She looked thoughtful. "Was your Amelia – Amy – was she..."
"No, no. I loved her dearly, but... She was married. To a brilliant guy. Waited two thousand years for her, he did. Couldn't have asked for a more romantic love story." They laughed – this could only be funny to two people like them. "But my Amy was glorious. And I know your Amelia will be, too."
The little alarm on The Doctor's watch beeped, and Rose's eyes finally filled with the tears he knew she'd been holding back. "Doctor..."
"Yes, Rose?"
"In another hundred years, will you come back and see us?"
"I'll do my best for you, Rose Tyler."
She wrapped her arms around him and hugged him tightly. His immediate response was to do the same, so thrilled to discover that she still fit against him despite the changes in his physiology. "Be safe, Doctor," she murmured against his shoulder.
"I will be," he replied, pressing a kiss to her hair.
They pulled apart, and she led him to the door. As their fingers parted and he walked down the path, he turned and looked back at the house. Rose stood on the porch, her pretty face streaked with tears. Upstairs at the window, Amelia and The Other Doctor waved, Amelia with a bright, happy smile; John with a sympathetic expression across his features.
The Doctor raised a hand and waved back, forcing a smile.
One hundred years and completely worth the wait.