"Loadstone testing now at 15.4," a voice on the loudspeaker announces as Donna and Rose enter a huge warehouse-like building, the base where Rose has been working with Captain Magambo. A circle of mirrors is set up in the middle, with wires and cords leading into that blue police box Rose knows so well. "Repeat, 15.4."

They approach Captain Magambo, who stands before a large computer; she salutes to Rose, saying, "Ma'am."

"I've told you," Rose sighs, "don't salute."

"Well, if you're not going to tell us your name…"

"What," Donna says, "you don't know either?"

"Crossed too many different realities," Rose explains as she checks the computer. "Trust me, the wrong word in the wrong place can change an entire casual nexus." Huh. Listen to her, talking all clever. All that time spent with the Doctor, Amelia, and Seth – they've rubbed off on her.

"She talks like that a lot," Captain Magambo says to Donna. "And you must be Miss Noble."

"Donna," Donna says.

"Captain Erisa Magambo. Thank you for this."

"I don't even know what I'm doing."

"Is it awake?" Rose asks the Captain.

"Seems to be quiet today," Magambo replies. "Ticking over. Like it's waiting."

She. Like she's waiting. Rose resists the urge to correct the UNIT Captain – these people are always referring to the TARDIS as 'it'. She humors them, for the same reason that she doesn't tell them her name. But she doesn't like it.

"D'you want to see it?" Rose asks Donna, but she's looking at the TARDIS.

"What's a police box?" Donna questions.

It's a TARDIS. That's Time and Relative Dimension in Space. It's a spaceship. It's a time machine. It's a doorway to the universe. It's home.

That's what she wants to say. But of course, she doesn't say any of it.

"They salvaged it from underneath the Thames," she says. "Just go inside."

"What for?"

"Just go in."

She watches, smiling knowingly, as Donna hesitantly enters the TARDIS. For a few seconds, there's silence, and then the redheaded woman's disbelieving voice comes from inside, shouting, "No. Way!"

Mouth hanging open, she gets out and walking around the outside of the box, and the hurries back in to see that it's really as huge on the inside as she'd thought. Then she steps out again and walks back to Rose, looking shocked.

"What d'you think?" Rose asks, grinning.

"Can I have a coffee?"

They get Donna her coffee, and together, the two women step inside the box.

Every time she walks inside, it's the very definition of bittersweet. It's beautiful, so wonderful and incredible and beautiful to see the place she calls home again. But it's so painful, so miserable, so achingly awful to see it devoid of light, of warmth, and of the Doctor.

"Time and Relative Dimension in Space," Rose tells Donna. "This room used to shine with light. I think it's dying." She touches the console lightly, and the Time Rotor moves just a bit. "Still trying to help."

"And…" Donna pauses. "And it belonged to the Doctor?"

"He was a Time Lord," Rose explains. "Last of his kind."

"But if he was so special, what was he doing with me?"

Rose shrugs and offers a small smile. "He thought you were brilliant."

"Don't be stupid."

"But you are!" she insists. "It just took the Doctor to show you that, simply by being with him." She looks away, remembering who she was before she met the Doctor – the young, dull shop girl, the dropout living with her mother, the one who nothing interesting ever happened to. "He did the same to me," she says quietly. "To everyone he touches."

"Were you and him…?"

Yes. No. I loved him. I think he loved me. Maybe someday.

"Do you want to see it?" Rose asks, touching Donna's shoulder gently.

"No," Donna replies immediately, but as Rose continues to look at her back, she relents. "Go on, then."

-0-0-0-

"We don't know how the TARDIS works," Rose says to Donna as they stand in the center of the circle of mirrors. "But we've managed to scrape off the surface technology. Enough to show you the creature."

"It's a creature?"

"Just stand here."

"Out of the circle, please," Captain Magambo calls.

"Yes, ma'am," Rose replies, and walks out of the circle.

"Can't you stay with me?" Donna calls after her, but before Rose has a chance to respond, Magambo calls out, "Ready? And… activate."

The lights around the circle switch on, flooding the area with bright light; frightened, Donna shuts her eyes.

"Open your eyes, Donna," Rose calls.

"Is it there?" the redhead asks shakily.

Rose's eyes drift to Donna's back, where, yes, she can see the large black beetle-like creature. It seems like it's clinging to her shirt, and Rose has to wonder how it stays on when Donna gets changed, but she supposes normal rules don't apply to it. After all, without the lights, the mirrors, and the TARDIS technology, you can't see or interact with it at all. "Yeah," she says. "Open your eyes, look at it."

"I can't."

"It's part of you, Donna. Look."

Slowly, Donna opens her eyes and looks at her back in the mirrors. When her gaze lands on the massive beetle, she starts to spin around in panic, trying to get a better view.

"It's okay, it's okay, it's okay," Rose says quickly. "Calm down. Donna?" No response from the redhead. "Donna? Donna!"

Eventually, Donna stops spinning, but her eyes are still wide. "Okay," Rose breathes.

"What is it?" Donna demands through labored breaths as she fights to remain calm.

"We don't know," Rose replies honestly.

"Oh," Donna spits sarcastically. "Thanks."

"It feeds of time," Rose explains, remembering what she's been told by Captain Magambo. "By – by changing time, by making someone's life take a different turn. Like, meetings never made… children never born… a life never loved. But with you, it's…"

"But I never did anything important," Donna insists.

"Yeah, you did," Rose says. "One day, that thing made you turn right instead of left."

"When was that?"

"Oh, you wouldn't remember," Rose tells her offhandedly. "It was the most ordinary day in the world, but by turning right, you never met the Doctor, and the whole world just changed around you."

"Can you get rid of – of it?"

"No," Rose says. "I can't even touch it. It seems to be in a state of flux." Listen to her, sounding clever again. Only this time she hasn't got a clue what she's talking about.

"What does that mean?" Donna demands, sounding fed up already due to the tiny bit of technobabble that Rose has subjected her to. How did she ever survive the Doctor, with his rambling and his genius-speak and his mile-a-minute rants?

"I don't know," Rose says with a laugh. "It's the sort of thing the Doctor would say!"

"You liar!" Donna accuses. "You told me I was special! But it's not me, it's this thing! I'm just a host!"

"No, there's more than that," Rose insists. "The readings are strange, it's… it's like reality's just bending round you."

"Because of this thing!"

"No, no! We're getting separate readings from you. And they've always been there, since the day you were born."

"This is not relevant to the mission," Captain Magambo interrupts. Typical UNIT, need-to-know and all that. Well, not for Rose.

"I thought it was just the Doctor we needed, but it's the both of you," Rose says strongly. "The Doctor and Donna Noble. Together. To stop the stars from going out."

"Why?" Donna demands. "What can I do?" There's a pause, and then, in a much softer, weaker voice, she requests, "Turn it off. Please."

"Captain," Rose says, and Captain Magambo announces, "Power down," and hits a button on the computer, and the lights go off. Rose steps into the circle and walks to Donna, touching her arm comfortingly.

"It's… it's still there, though," Donna stammers. "What can I do… to get rid of it?"

A small smile grows on Rose's face as she replies, "You're gonna travel in time.

-0-0-0-

"The TARDIS has tracked down the moment of intervention," Rose says, and she can't help but marvel at how very like the Doctor she sounds. "Monday the twenty-fifth, one minute past ten in the morning. Your car was on Little Sutton Street leading to Ealing Road, but you turned right heading towards Griffin's Parade. You need to turn left. That's the most important thing. You've got to go back, turn left. Have you got that, Donna? One minute past ten, make yourself turn left, heading for the Chiswick Highroad."

"Keep the jacket on at all times," Captain Magambo says, speaking of the coat Donna is wearing – strange-looking, all full of wires and such. "It's insulation against temporal feedback." As an officer puts a kind of a watch on Donna's wrist, Magambo says, "This will correspond to local time wherever you land." And then she hands Donna a glass full of water, saying, "This is to combat dehydration."

After Donna's sipped a bit of the water, the three of them plus several UNIT soldiers walk to the circle of mirrors.

"This is where we leave you," Rose says.

"I don't want to see that thing on my back," Donna warns.

"No," Rose agrees. "The mirrors are just incidental. They bounce chronon energy back into the center, which we control to decide the destination."

"It's a time machine," Donna summarizes incredulously.

Rose smiles, and repeats back, "It's a time machine."

"If you could?" Captain Magambo requests, and Donna walks into the center of the circle. "Powering up."

The lights turn on, and Donna asks, "How d'you know it's gonna work?"

"Hmm?" Rose looks up. "Oh… yeah… we, we don't. We're just… we're just guessing."

"Yeah," Donna replies with a sarcastic little laugh. "Oh, brilliant!"

"Just remember," Rose says, "when you get to the junction, change the car's direction by one minute past ten."

"How do I do that?"

You run in front of a truck. You get hit. You die. "It's up to you."

"Well, I just have to… run up to myself, and… have a good argument."

Rose laughs. "I'd like to see that!" But I won't. Instead, I'll see you die.

"Activate loadstone," Captain Magambo calls.

"Good luck."

"I'm ready!" Donna says brightly.

"One minute past ten."

"'Cause I understand now," she continues, sounding slightly scared but full of hope. "You said I was gonna die, but you mean this whole world, it's gonna blink out of existence. But that's not dying. Because a better world takes its place. The Doctor's world. And I'm still alive! That's right, isn't it? I don't die? If I change things, I don't die?" She looks to Rose for reassurance, and Rose tries to keep the sorrow off her face, but she's never been good at putting on a mask. And she knows that Donna can tell she's wrong. "That's… that's right, isn't it?" she asks again, edging into desperation.

"I'm sorry," Rose says, softly, regretfully.

"But I can't die!" Donna insists. "I've got a future! With the Doctor! You told me!"

"Activate!" Captain Magambo shouts. Sparks fly; a white light engulfs Donna, and when it fades, she's gone.

And Rose is gone, too, not long after.

-0-0-0-

The next time Rose comes through, she's in a small, run-down neighborhood that she recognizes from the photos UNIT showed her as Donna's home in Leeds. And it's not long before Donna herself walks around the corner and sees Rose. "Hello."

"Hi," Rose replies, perfectly casual, but all she can think is, I watched you die.

Huh. Seems like she's better at putting on a mask than she thought.

They walk together to a park bench in silence, and Rose subtly checks her dimension cannon for the time and date. She thinks back to the timeline that Captain Magambo showed her, and in her mind, she finds the date.

Ah, yes. This is right in the middle of the ATMOS crisis, then. Right before Gwen and Ianto give their lives, and Jack… oh, Jack…

"It's the ATMOS devices," Rose explains as they sit. "We're lucky, it's not so bad here. Britain hasn't got that much petrol. But all over Europe, China, South Africa, they're getting choked by gas."

"Can anyone stop it?" Donna asks.

"Yeah," Rose replies. I watched you die. "They're trying right now, this little band of fighters, on board the Sontaran ship." She looks up at the sky and murmurs, "Any second now…"

And indeed, the moment she finishes speaking, flames burn across the night sky. They illuminate the world below briefly, and then they fade, and all is dark again.

"And that was?" Donna asks, sounding shocked.

"That was the Torchwood team," Rose replies sadly. "Gwen Cooper, Ianto Jones, they gave their lives. And Captain Jack Harkness was transported to the Sontaran home world." Oh, Jack… poor Jack, her best friend, her brother. Trapped in this eternal purgatory. Because of her. And Gwen and Ianto, dead because the Doctor wasn't here. It hurts all the more, that thought, because she did know Ianto very well. They never really acknowledged it, either of them, but they bonded over that shared pain in their eyes. Neither ever asked the other about the reason for that pain. They communicated in coffees and bear claws, in murmurs of "Thanks" and brief hugs for no reason at all. He was a friend, a comrade, someone who somehow knew what she was going through. And now he's gone.

It isn't the same Ianto, of course. And he'll be back soon, just as soon as Donna sets everything right (which Rose knows she will, having already experienced it). But still. In this universe, in this moment in time, Ianto Jones is dead. "There's no one left," Rose whispers.

"You're always wearing the same clothes," Donna notices. "Why won't you tell me your name?"

"None of this was meant to happen," Rose murmurs. "There was a man. This wonderful man, and he stopped it. The Titanic, the Adipose, the ATMOS, he stopped them all from happening."

"That… Doctor?" She is clever in her own way, Donna Noble is. She's caught on quickly.

"You knew him," Rose tells her.

"Did I?" Donna frowns, puzzled. "When?"

"I think you dream about him sometimes," Rose continues. "A man in a suit. Tall, thin man, great hair…" She allows herself a soft laugh. I watched you die. "Some really great hair."

"Who are you?"

"I was like you," Rose replies simply. "I used to be you. You've travelled with him, Donna. You've travelled with the Doctor in a different world."

"I never met him, and he's dead."

"He died underneath the Thames on Christmas Eve," Rose agrees, "but you were meant to be there. He needed someone to stop him, and that was you. You made him leave. You saved his life." I watched you die.

For a moment, something flickers in Donna's eyes, and Rose thinks that perhaps she remembers. But that flash is gone in a moment, and Donna snaps, "Stop it. I don't know what you're talking about, leave me alone!"

"Something's coming, Donna," Rose says. "Something worse."

"The whole world is stinking," Donna points out viciously. "How can anything be worse than this?"

"Trust me," Rose pleads. "We need the Doctor more than ever. I've been pulled across from a different universe, because every single universe is in danger. It's coming, Donna. It's coming from across the stars and nothing can stop it."

"What is?"

"The darkness."

"Well, what do you keep telling me for?" Donna demands in frustration. "What am I supposed to do? I'm nothing special. I mean, I'm… I'm not, I'm nothing special. I'm a temp. I'm not even that, I'm nothing!"

Rose laughs. "Donna Noble, you're the most important woman in the whole of creation."

"Oh, don't," Donna breathes. "Just… don't. I'm tired. I'm so… tired."

"I need you to come with me."

"Yeah," Donna scoffs. "Well, blonde hair might work on the men, but you ain't shifting me, lady."

Rose smiles. I watched you die. "That's more like it."

"I've got plenty more," Donna assures her."

"I know you'll come with me," Rose says, softly but confidently. I watched you die. "Only when you want to."

"You'll have a long wait, then."

Rose thinks of the times she saw on her dimension cannon, quickly calculating the time between now and when Donna turned to her and said she was ready. "Not really, just three weeks. Tell me, does your grandfather still own that telescope?"

"He never lets go of it," Donna replies softly.

"Three weeks' time," Rose repeats. I watched you die. "But you've got to be certain." She remembers what Donna said to her – 'You said I was gonna die.' "'Cause, when you come with me, Donna… sorry… so sorry, but… you're gonna die."

I sent you to your death. I watched you die.

And then the dimension cannon has one of its moment where it opts for a route apart from that of blue lightning and pain, and grants her a smooth transition back to the other universe.

And she fades away in front of Donna Noble's eyes.

-0-0-0-

Sorry if this is a bit confusing - I decided to jumble up the order of events in Turn Left so that all of the foreknowledge Rose always seems to have would make sense. I put a lot of thought into the order, so I hope it makes sense.