It was a lovely warm day and they were in London (again) instead of Rio (again) but so far there didn't seem to be any aliens or catastrophes, so Amy found herself willing to compromise. A day of peace, even if it was basically still at home.

She was happy, walking down the street with her boys, in the full light of an unusually glorious spring day, full on chips and soda and holding hands with Rory while the Doctor padded along beside them, chattering inanely.

"The airspeed velocity of an unladen swallow…" he was just saying now, and Rory was nodding along, and Amy was on the point of telling him to shut up, when he did stop, quite suddenly.

"Doctor?" she said, but he didn't reply.

She gripped Rory's hand, reveling in the feel of her husband's palm against her own, and threw him a glance. He shook his head—no, I don't know what he's doing either—and then she moved in closer to see what it was that had arrested his attention.

His eyes were fixed in the middle distance, and there, glowing in the sunlight, was a woman. She was beautiful, with wide cheekbones and a full mouth and voluptuous curls in her hair, which was shining gold under the bright light. Dressed very well indeed, checking a cell phone as she hurried through the park. Lovely, Amy thought, certainly pretty enough to catch a man's notice, but she looked sad somehow.

"Doctor?"

He started. "What?"

"Who's that?"

"Who's who?" he replied evasively. She scrutinized him as his eyes darted left and right, searching for an escape.

"That girl," she forged on. He swallowed.

"What girl?"

"That—"

Except the girl was gone. She must have turned a corner, crossed the street, something, because now her golden head of curls was nowhere to be seen, and the Doctor was wearing a look of smug relief.

She glared at him, full with the all the force of her Scottish wrath. "Fine," she said, "You escaped. This time."

She overhears him, though, later, in the Tardis' library, saying a name aloud to himself.

"Rose Tyler."

It is with some trepidation that Amy runs a Google search on the name, just as soon as they can get to a place on early twenty-first century Earth with internet access. A few things flash up. An ad for a spa with a stupid, flowery name. A news report about a department store that blew up a few years ago—Amy'd heard of that, actually, they'd said in school that it had been terrorists—a "have you seen this person" website, and a list of the casualties of a major structural collapse at Canary Wharf.

And pictures. One from a high school yearbook, of that same beautiful blonde woman, but younger and more carefree. She clicked through to the website and discovered a webpage.

"Rose, We Love You" it was titled. It was an entry on someone's blog, a girl called, apparently, Shireen.

Today they published the list of the dead from Canary Wharf, Shireen had written. My best friend was on that list.

With a growing sense of misgiving, Amy read on, and as she did her eyes welled with tears.

I've known Rose since we were little kids…played together in the sandbox…skipped classes together…

One day she ran off with this guy, and we thought we'd never see her again, but she did come home. I remember being so angry, but then she told me about him and I couldn't hold it against her. "He's given me the stars," she said. That's when I knew Rose had fallen in love…

There were more pictures. The same beautiful blonde woman, but much younger, so much happier. She was dressed in the most sequined dress Amy'd ever seen, and she was dancing with two other girls, watched by a smiling boy. Rose, Mickey, Keisha and me, New Years 2003, the picture was captioned. Another of just the girl and boy, holding hands by a fountain, with wind blowing her hair to stick in her lip-gloss, spread across a wide grin. There was so much life in her bright eyes. Rose and Mickey.

Rose, it went on, we love you so much. We love you, and we miss you. We will always remember you, and the time we had together. We know you were happy, and we are so proud of you.

Rest in Peace, Rose Tyler.

The words glowed on the screen with a beautiful picture of Rose with a skinny man with brown hair and a woman who was presumably her mother, and tears hit the keys of the café computer.

Amy wasn't actually looking for the door when she found it. After the crying in the café incident she'd backed off pretty quickly on her self-imposed mission. It was possible, she told herself, that the Doctor had just been surprised because he saw a Rose-Tyler-look-alike, though how he'd known Rose himself was a mystery.

Maybe he'd been the man from Shireen's blog who'd spirited her away. It was the kind of thing he did, and she would know.

She sighed and reached for the library door. The Doctor had been melancholy lately, more down-trodden and less bouncy. It was passing odd, and it just didn't stop. Usually if he was in a funk it ended after a few days, but weeks were stretching on now. Even Rory had noticed.

The handle turned with a click and Amy padded into the room beyond, lost in her musings about the state of her family.

But it wasn't the library. The library was cavernous and smelled like books and wood and chlorine. The first impression she got of this room was of light. The second was of pink, and the third was of the smell of very particular kind of citrus-like tree she couldn't remember the name of from some pretty little planet in the next galaxy over.

It was a girl's bedroom. No bunk beds, Amy noted a little bitterly, as she made her way around the room. Pink walls, though more a warm orchid than the vivid magenta she'd first assumed. The bed was covered with a crazy quilt, a shelf by the bed was loaded with romance and history books in a multitude of languages, and the vanity mirror was stuck full of pictures.

It was Rose, with that skinny brown man, and her with another guy with big ears, who was scowling in one shot, but grinning like a loony in another. Her with her mother, with Mickey, the picture from the website of her at a New Years. What seemed like a hundred beautiful landscapes captured in film, some with people, some with Rose, others empty but for boundless skies in all the colors of the rainbow, red and pink and green and purple.

Something caught Amy's eye about those grins. The big-eared man, the skinny but terribly swotty one, wearing identical mega-watt smiles, clearly over-brimming with joy and wonder at the universe. The same grin she saw on her Doctor's face sometimes. A child staring into time and space and adoring every second.

She crept closer to the vanity, fingering the edge of one of the photos. In the pictures before the two men, her eyes were bright. After them, her eyes couldn't have shone more brightly than the stars themselves.

On the vanity there were more photos in frames, mostly older snapshots of family and friends, by the looks of things. Some jewelry, some of it cheap and clearly from Earth second-hand shops, some of it exotic and beautiful. A dog-eared copy of Pride and Prejudice, nail varnish, and a chunk of space rock holding down pile of papers. And in pride of place was little jewelry box, covered in red velvet and miraculously free of dust.

The box made no sound as it was snapped open.

On the bed of crimson it lay like a nebula frozen solid, a glittering, indistinct, glorious little thing. The stone was the size of the nail on her little finger, long and flat and shimmering to perfection, set against a silver band. The interior had an inscription in Latin, Aeternum, and it took a moment for the translation matrix to allow her to read the word, Eternity. It took her but a moment to realize that Rose had never seen this ring, because it sat with a few other relics. A hair-band, a mug, and a picture of Rose by herself were all arranged together, and the ring had sat dead center. There was no wear on the metal—it had never touched her skin. This was a shrine, Amy realized, and her stomach twisted at the thought of disturbing the Doctor's place to grieve, but how else was she to learn?

She looked back at the photographs of the men. They never appeared together. Sometimes alone, sometimes with Mickey, more often with Rose, but never together. And that grin.

"Are they him?" she wondered aloud. They had the same old, old eyes, though neither looked as destroyed as her Doctor did. Could they be him? And how on earth did he manage to change his face so completely? She scowled at the pictures. "Library," she said decisively, and turned to leave the room.

It was called regeneration, a process whereby a Time Lord who had suffered a mortal injury could "re-boot" themselves completely, from the genetic level. It was quite traumatic the first few times, apparently, but then a well trained Time Lord could usually choose his or her form and would suffer considerably less regeneration sickness.

Regeneration was evidently what the Doctor had still been going through when she'd first met him, when he was "still baking", a comment she hadn't understood at the time.

And Rose had known him in two regenerations, it seemed. The big-eared one, and the gorgeous one with the fabulous hair. And he'd loved her, all three of him.

Amy watched him flirt half-heartedly with River and sighed inside. She loved her little girl, wanted desperately for her to be happy, but the memory of the nebula ring haunted her.

Aeternum. Eternity.

The Tardis was rather closer to Amy than she ever was to Donna, though she loved her dearly, or Martha, who didn't quite understand. Perhaps only the Doctor and River could fly her, but Amy could certainly get her help in weaseling out information. Especially since she'd started deciphering the case of the mysterious blonde, now known to be Rose Tyler.

It took almost no effort whatsoever on Amy's part to wheedle some records out of her databanks, even less for her to convince the Tardis to lock the boys out for the evening so she could get into those records and find out what they meant in the great saga of Rose Tyler. So what if the old girl couldn't talk? That didn't make her any less Amy's ally and friend.

Rose was cheeky, she learned. An estate girl from London, just about Amy's age, or a year or so older. She'd first come with the Doctor after helping to save London from an army of shop window dummies. Her first Doctor had been older looking, with big ears and a gruff manner, who spoke with a Northern accent and wore a leather jacket as though it was a suit of armor.

Then something had happened involving a conspiracy of Daleks and the handsome Captain Jack, and Rose had torn open the heart of the Tardis in order to save them all.

The Doctor had regenerated saving her life, absorbing the rest of the Time Vortex so she wouldn't have to die. This new man was younger, happier, and altogether more bizarre. He liked to say things like allons-y and molto bene and lick substances of dubious origin in order to identify them. His accent had gone as well, and according to the Tardis it was because this regeneration was actually patterned on Rose.

The Doctor was unusual, Amy had discovered, because he didn't choose the forms he regenerated into. The Tardis said it was because he'd done a bunk before they'd got that far in the Academy, running away on some freak adventure, and when they'd dragged him back he never made up the lesson.

The sheer normalcy of that staggered Amy, who'd done much the same thing with variables in mathematics, and the idea of her nerdy Doctor skiving off school was almost as funny as the goofy grin he wore in photographs with Rose.

Rose and her second Doctor had bopped `round the cosmos for nearly a year, before Canary Wharf happened.

Rose wasn't dead, Amy discovered. She was trapped in another universe with a half-human clone of the last Doctor. Just for that, Amy resolved to smack the Time Lord around a bit. Trust him to try and stop a girl making her own choices.

And now, inexplicably, she was back. Alive and walking around central London dressed to kill. Amy sighed as she rewatched a clip from the Tardis archive, of Rose and Leather-Jacket dancing round the console to "In the Mood".

If she was in this universe, why on earth hadn't she found him yet?

It was another lovely day, summery and sunny, and Amy was walking with Rory when she saw her.

A bouncing mane of caramel curls over a suit jacket and jeans, bag over shoulder, the posture of someone checking their cellular device as they walked down the street.

"Come on, hurry," she muttered at Rory, and tugged him along as she tried to catch up with the blonde.

Slowly but surely they gained on her, and Amy held her breath as she reached out and caught the woman's arm.

"Amy—" Rory started, shocked.

"Wait—" she called, and the blonde woman turned, eyes wide.

She was a bit older than she'd been in the photographs, less makeup, but definitely her.

"Can I help you?" Rose asked.

"You're Rose Tyler."

"How'd you know that?"

"We travel with the Doctor."

A moment of breathless silence.

"Is he—"

"D'you—"

Again the two women stared at one another.

"Come home," Amy said.

"Run," said Rose.

The look on Rose's face as she caught sight of their shared home made every second of the time she'd spent worth it.

Amy snuggled closer to Rory on the loveseat in the library, eyes half-closed as she watched the other couple.

Rose and the Doctor were huddled together in the other loveseat, something that had appeared in place of his armchair the first time Rose had seen the new library. They were talking in low voices, her eyes closed, him watching her with a wondering, adoring look. On her finger glittered the nebula ring, which every now and again one of them would touch, as though it were the keystone.

"He really loves her," Rory said quietly.

"Yeah," Amy answered sleepily. "He does."