She hates that. She's got out of the habit of admitting she doesn't know something (a talent which has come in handy when the people at Torchwood look at her with something akin to hero-worship), and she wants that invincible feeling back. But deep down, she knows that it was only a by-product of TARDIS travel. Alien languages translated in your head, and a shot of Doctor-inspired courage that fades every day she spends away from him.
(And didn't that come as a shock, when she first came into contact with this world's aliens? She walked up to them, fearless in her mission to negotiate, only to find she couldn't understand a word they said - if, indeed, they were using words. She almost cried that day; it was the closest she'd been since the incident.)
So now she's staring at a screen full of numbers she doesn't understand, pulling random observations out of the air like rabbits out of a hat, and she really hopes that this doesn't go as badly as the last time she tried to talk her way out of a situation.
Don't you wanna know? What happened to the Emperor?
The power cuts off without warning, and her voice falters. Mickey, ever the hero, jumps in to continue her non-explanation, and she thanks every God she's ever heard of that Sarah Jane made him take that step into the TARDIS.
The first day away from 'home', she makes a mistake which almost ends the world.
It's a routine check-up for all Torchwood offices, Pete/Dad says. (His name depends on her mood, and she's a bit lost at the moment.) All she'd have to do is turn up in Cardiff, do a meet-and-greet, and watch them run a systems check. Nothing to worry about; she'd be home by teatime.
Of course, no such thing happens. Someone pushes the wrong button, and suddenly the Rift is splitting Cardiff in two. As senior agent, she's in charge, and suddenly she has no bloody clue what to do because she can't be the Doctor on this one; she can't bluff her way out. All she can do is stand there and watch their resident computer genius engineer some sort of electromagnetic field that she can't even pronounce while the rest of the team begin damage control.
It's a mess. Two people die (the computer girl and her sort-of-boyfriend, the team medic) because when they go out on the streets to capture the Weevils that had escaped the sewers, Rose hesitates a bit too long over allowing the use of guns. In the end, she has no choice; two of them are dead and the second-in-command snaps and shoots three Weevils between the eyes before Rose can blink.
When she gets 'home', she goes straight to the Torchwood office to pick up the standard-issue gun she swore she'd never use. Then she takes it to the firing range and stays for hours, shooting over and over until her aim is perfect. Because the one thing that day taught her is that not everyone has thirteen lives; the good guys don't always make it out alright and sometimes pulling the trigger yourself is better than letting someone else pull it for you.
She's learnt a lot in the year-and-a-half she's been away. (Who'd have thought it - Rose Tyler, renowned rejector of all things scientific, spending her lunch breaks with physicists trying to learn temporal engineering? But honestly, what else could she do when the first book she picked up in the library was - completely by chance - Time Travel - The Reality published by Bad Wolf Corporations?)
And one of the things she's learnt is that when Agent Jovanka says 'jump', you don't bother asking 'how high?', you just throw yourself out of the nearest window. So when Jovanka tells her to get her warm clothes on because she's going to mid-winter London in a parallel world, she doesn't question it during the briefing. Of course, that's more than enough time to pique her curiosity, and she can't help wondering if it has something to do with the recent disappearance of the stars.
The mission turns out to be incredibly short. She visits an Internet cafe, meets a ginger woman and watches the police fail to manage a crowd, then simply fades back into her world. (She's not quite sure when it stopped being 'the other world' and became 'her world'. She's also not sure whether she likes it.) She delivers the information she downloaded from the Internet to the Torchwood computer squad, then goes back to Jovanka to find out what the hell that was all about.
Jovanka, rather uncharacteristically, explains. The stars are going out because of some strange readings they've picked up, converging on a parallel world. Conveniently, some world-hopping equipment turned up in Stoke the week before (too conveniently, Rose would have said, had there not been a small wolf's head motif engraved into each metal corner), and as it was well-known that Rose was intimately familiar with parallel worlds, her name had been put forward for the job. Oh, and the tech guys needed some help sifting through the information - would she mind?
Donna Noble? Who the hell is Donna Noble?
There's a slight flash of jealousy as Rose scans the information. It turns out her little gadget did more than download the Internet; it had pulled the files of every computer in Britain. So now she's sifting through a stack of paper, trying to find anything that would connect this whole mess to the Doctor and tell her where to find him. So far, she's got a string of names, but none of them seem to be current.
This last one is different, though. U.N.I.T. intelligence suggests she's the latest 'companion' and when Rose turns the page, she recognises the photo. That ginger woman from her three-weeks-ago spacehop. Dammit! She had been so close.
She makes a note of the information she's found, and quickly scans the rest of the file. She's got as far as Donna's grandad's army service record when one of the temps (Lisa? Lucie?) comes running in.
"Miss Tyler? Miss Tyler, we've found an anomaly. Agent Jovanka wants you in her office now."
As it turns out, the 'anomaly' is one Miss Donna Noble in a world that shouldn't exist. And to fix it, Rose will have to convince a parallel U.N.I.T. that using the TARDIS for temporal engineering is a really clever idea, and she should be put in charge. Thank God for those lunches.
So Rose sets off to restore the balance of the world. And although the woman seems irritating beyond belief, her little speech in the mirror circle has Rose almost in tears because after months of pretending, she's finally become a little bit Doctor. She can see the woman the Doctor saw and it's not fair that Donna should have to step out in front of a truck. And she feels like such a bitch, because part of her is just a little bit glad. Two words whispered and the Doctor will know she's coming (home?) back.
She probably could have found another way that didn't involve Donna's death. But this is quicker, and easier, and a million other things that never would have mattered when she was an idealistic shop girl.
Sometimes she misses that girl. Then she remembers how the Doctor sent her away from the Game Station, and was prepared to sacrifice Jack for the 'greater good', and she just gets confused.
Final world-jump. She's almost ready.
She's tried, she really has, but she can't stop herself. She has to take the gun, because when she's without it all she can see are those people from Cardiff who died because she was scared that a man a whole Universe away would disapprove. He'll have to take her as he finds her now; she's not the same as she was. The gun is a part of her, and there's more at stake than a disappointed frown.
Last call. Good luck, Miss Tyler. See ya, Mickey. Bye, Rose. Love you, Mum.