Old Companions

Travelling with the Doctor was…wonderful. They hadn't gone on many adventures since Caroline had been declared one of his apparently "official" companions, but the ones they had gone on had been amazing. Donna would be the companion to speak, to engage with alien races, and Caroline would be the one building a small database of alien races for herself.

Now, the Doctor was attempting to teach Donna how to fly the TARDIS. He'd asked if Caroline wanted to try, saying that the TARDIS flight would be smoother with multiple people, but she'd declined. There was a reason she didn't actually own a car, after all.

Well, there was another reason she didn't own a car.

But she wasn't going to think about that, not right then. She wouldn't do that to herself.

At that moment, Caroline was leaning against one of the Y-beams of the TARDIS, since the Doctor had informed her it would probably be safer to stay far away for at least the start. Even he didn't know what would spark if Donna or he messed something up.

"I can't believe I'm doing this!" Donna cheered as she worked, the Doctor stood next to her.

"No, neither can I," he mumbled. "Oh, careful." Lurching forwards, the Doctor hit the console with a mallet and took control for a few minutes. Caroline laughed. To think that in order to fly a time machine you needed to hit it with a mallet. "Left hand down. Left hand down! Getting a bit too close to the 1980s."

The TARDIS had been shaking the entire time but, then, it lurched quite suddenly and Caroline stumbled off the Y-beam.

"What am I going to do," Donna sighed, "put a dent in them?"

"Well, someone did."

A phone rang from somewhere on the console, close to where Caroline had stumbled. "Hold on," Donna said, frowning. "That's a phone." Caroline pulled what looked like a modern day mobile from a socket in the console. "You've got a mobile? Since when?"

"It's not mine." There was something solemn about the Doctor's voice, like the fact this phone was ringing was bad, meant something was going wrong. Caroline handed it to him carefully, watching his face as he leaned back to answer it. "Hello?"

|C-S|

The phone call turned out to be from the Doctor's previous companion, a one Martha Jones. He'd left her upon her own request, the Doctor had been certain to tell them back. Apparently she'd left the phone with him with the promise that, if it ever rang, he would answer immediately.

He had told them about Martha. Whenever they met an alien race he'd visited with her, he would mention it. But he hadn't told them why she had wanted to leave.

When they apparently materialized where Martha was, the Doctor was the first one out. Donna and Caroline had decided to give him a little time to greet his old companion before they were introduced. That didn't mean they weren't listening into the conversation, of course. Both of them were quite curious people, after all.

It was why they worked so well together.

"Martha Jones," he said, almost apprehensive.

"Doctor," Martha replied. There were a few moments where the two were either walking or staring at each other before Donna peaked her head out and spotted them hugging.

"You haven't changed a bit."

Martha laughed. "Neither have you."

"How's the family?"

"You know. Not so bad. Recovering."

Donna and Caroline stepped out then, Donna first. "What about you?"

Martha, however, didn't answer him. She just looked over her shoulder to the two of them. "Right." She nodded, swallowing. "Should have known. Didn't take you long to replace me, then. Just didn't expect there to be two."

The Doctor stepped back, holding out his hands to the three of them. "Now, don't start fighting. Martha, Donna. Martha, Caroline. Donna, Martha. Caroline, Martha." He pointed at each of them each time he said their name. "Please don't fight. Can't bear fighting."

Donna laughed, walking forwards. "You wish." The two of them shook hands. "I've heard all about you. He talks about you all the time." Caroline nodded.

"I dread to think." She shook Caroline's hand as well.

"No, no, no. No, he says nice things. Good things. Nice things. Really good things."

Martha sighed. "Oh my God. He's told you everything."

Donna grinned. "Didn't take long to get over it though. Who's the lucky man?"

"What man? Lucky what?" Caroline nearly laughed at the Doctor. Martha had, most likely intentionally, brushed her hair aside with the hand she had an engagement ring on, something she'd once seen a previous acquaintance doing.

"She's engaged, you prawn."

The Doctor frowned. "Really? Who to?"

"Tom. That Tom Milligan. He's in pediatrics. Working out in Africa right now. And yes, I know, I've got a doctor who disappears off to distant places. Tell me about it."

"Is he skinny?" Donna asked, making the Doctor nod as if it was an important question to ask.

"No," Martha shook her head, "he's sort of strong."

"He is too skinny for words. You give him a hug, you get a paper cut."

The Doctor sighed as the three of them chuckled, though Caroline couldn't really get upset. She'd been told multiple times that she was so small that she would get crushed in a hug, even if she wasn't really that tiny. About the size of Martha, really. "Oh, I'd rather you were fighting."

Martha's walkie-talkie crackled. "Speaking of which."

"Dr. Jones, report to base, please. Over."

"This is Dr. Jones. Operation Blue Sky is go, go, go. I repeat, this is a go."

They followed her down the alley onto a main road, where a convoy of jeeps and trucks were just traveling past. "Unified Intelligence Taskforce. Raise that barrier, now!" The soldiers entered a factory a little further away. "Leave those safeties on, lads. They're non-hostiles."

"All workers, lay down your tools and surrender," another soldier called, though this time through a bullhorn, as the soldiers stormed the factory.

"Greyhound Six to Trap One. B Section, go, go, go. Search the ground floor. Grid pattern Delta."

Caroline leaned forwards, the fact she was the one speaking making Martha jump a little. "What are you searching for?"

"Illegal aliens."

"This is a UNIT operation. All workers lay down your tools and surrender immediately."

Martha ran off, leaving the three of them outside the factory. "B section mobilised. E section, F section, on my command."

"Is that what you did to her?" Donna asked, watching her go. "Turned her into a soldier?"

|C-S|

A little while later, after they'd seemingly taken the factory, Martha returned to them. "And you're qualified now. You're a proper doctor." The Doctor nodded at a badge.

"UNIT rushed it through ,given my experience in the field. Here we go." They started walking again. "We're establishing a field base on site. They're dying to meet you."

"Wish I could say the same," he whispered to his current companions.

They entered through the back of a large mobile base, seemingly inside a truck. The room inside was full of all sorts of high tech equipment, almost exactly a military base from the movies. "Operation Blue Sky complete, sir." Martha approached an older man who must have been highly ranked, given his uniform. "Thanks for letting me take the lead. And, this is the Doctor. Doctor, Colonel Mace."

Mace saluted. "Sir."

The Doctor very nearly grimaced. "Oh, don't salute."

"But it's an honor, sir. I've read all the files on you. Technically speaking, you're still on staff. You never resigned."

Caroline looked around at the room. "You used to work for them?" It was partially the current presence of the Doctor that helped her speak, but also just the influence of spending time around him and Donna. She'd always had talkative friends, but there was something about running from alien threats and traveling through time that helped her speak at least a full sentence without feeling sick.

He shrugged. "Yeah, long time ago. Back in the 70's. Or was it the 80's? But it was all a bit more homespun back then."

"Times have changed, sir."

"Yeah, that's enough of the sir."

"Come on, though, Doctor. You've seen it. You've been on board the Valiant. We've got massive funding from the United Nations, all in the name of Home World Security." Martha brought them around the first rows of desk to better see the computers.

"A modern UNIT for the modern world."

Donna looked at him with what had become her trademark expression. "What, and that means arresting ordinary factory workers, in the streets, in broad daylight? It's more like Guantanamo Bay out there. Donna, by the way. Donna Noble, since you didn't ask. I'll have a salute."

Mace looked at the Doctor first, who nodded at him expectedly, and Mace saluted Donna. "Ma'am."

Donna nodded, satisfied. "Thank you."

Mace turned to Caroline, who blushed. "I'm Caroline Attwater. I…I don't need a salute."

"Tell me," the Doctor interrupted, like he tended to do when Caroline was obviously either overwhelmed or upset, "what's going on in that factory?"

"Yesterday, fifty two people died in identical circumstances, right across the world, in eleven different time zones." The map showed the locations as he said them. "Five a.m. in the UK, six a.m. in France, eight a.m. in Moscow, one p.m. in China."

Caroline swallowed, fighting a dry mouth. "You mean they died simultaneously." The Doctor had told her to speak whenever she had an observation, he would help if the words were difficult. Even now, especially surrounded by so many people and speaking so much in quick succession, her voice shook, but the Doctor nodded in encouragement.

Mace nodded as well. "Exactly. Fifty two deaths at the exact same moment, worldwide."

"How did they die?"

"They were all inside their cars."

"They were poisoned," Martha said, which made the Doctor look up. "I checked the biopsies. No toxins. Whatever it is, left the system immediately."

"What have the cars got in common?"

"Completely different makes. They're all fitted with ATMOS, and that is the ATMOS factory."

The Doctor frowned. "What's ATMOS?"

"Oh, come on," Donna scoffed. "Even I know that. Everyone's got ATMOS."

Caroline had read into ATMOS when it had first been introduced, just as she'd done with Adipose. And it worked. It was ingenious, and it worked.

|C-S|

Martha brought them along a catwalk above the factory floor, Mace following them all up. "Stands for Atmospheric Omission System. Fit ATMOS in your car, it reduces CO2 emissions to zero."

"Zero? No carbon, none at all?"

Donna nodded. "And you get sat-nav and twenty quid in shopping vouchers if you introduce a friend. Bargain."

"And this is where they make it, Doctor." Mace gestured to the factory. "Shipping worldwide. Seventeen factories across the globe, but this is the central depot, sending ATMOS to every country on Earth."

"And you think ATMOS is alien."

He shrugged. "It's our job to investigate that possibility. Doctor?" Mace brought them down a corridor to a sectioned off office where they appeared to have laid out an ATMOS device for examination. "And here it is, laid bare. ATMOS can be threaded through any and every make of car."

"You must've checked it, before it went on sale." The Doctor also glanced at Caroline.

Martha nodded. "We did. We found nothing. That's why I thought we needed an expert."

"Really. who'd you get?" He looked at all of them, sliding on his specs, but they just waited for it to sink in. "Oh, right. Me, yes. Good." Mace and Martha left the room, leaving the trio to examine it. "Caroline?"

She'd explained her tendency to research technology and try and understand the scientific component to most things. But it was amusing that he wanted her to clarify, since she understood what he meant when he asked. "Works perfectly. The creator, Rattigan Academy, has refused to publicly disclose much, and no one has reported being able to examine the devices besides UNIT."

"And?"

She shrugged. "I don't drive." She'd heard good things about ATMOS, and most people had it in their cars, but she'd never actually had it herself.

Donna nodded. She'd learned to keep quiet when Caroline wished to speak, letting her get out her thoughts. But, if it got difficult, both the Doctor and Donna were perfectly willing to jump in and take over the conversation, letting Caroline fade into the background and calm herself again. "So why would aliens be so keen on cleaning up our atmosphere?"

He picked up the device, Caroline next to him. "A very good question."

"Maybe they want to help. Get rid of pollution and stuff."

"Do you know how many cars there are on planet Earth? Eight hundred million. Imagine that. If you could control them, you'd have eight hundred million weapons."

Donna's eyes widened. "Oh my God."

Mace and Martha walked back in, passing Donna on her way out. The Doctor bent over the device, Caroline leaning against the table next to him. She didn't know anything about how to tell if a device was alien or not, but it was interesting to see, none the less.

"Ionizing nano-membrane carbon dioxide converter," the Doctor told them. "Which means that ATMOS works. Filters the CO2 at a molecular level."

Mace shook his head. "We know all that, but what's its origin? Is it alien?"

The Doctor sighed. "No. Decades ahead of its time." He glanced up at Mace. "Look, do you mind? Could you stand back a bit?"

Mace frowned. "Sorry, have I done something wrong?"

The Doctor nodded at the man's hip, where he had quite an advanced gun. "You're carrying a gun. I don't like people with guns hanging around me, all right?"

"If you insist." Mace strolled to the far side of the room, looking a bit offended.

"Tetchy."

He shrugged. "Well, it's true."

"He's a good man."

The Doctor straightened, flashing his sonic at the ATMOS. "People with guns are usually the enemy in my books. You seem quite at home."

"If anyone got me used to fighting, it's you." Martha looked at Caroline then, who crossed her arms.

"Oh right, so it's my fault."

"Well, you got me the job. Besides, look at me. Am I carrying a gun?"

The Doctor glanced at her. "Suppose not."

"It's all right for you. You can just come and go, but some of us" she looked towards Caroline "have got to stay behind. So I've got to work from the inside, and by staying inside, maybe I stand a chance of making them better."

He smiled. "Yeah? That's more like Martha Jones."

Martha grinned. "I learned from the best."

"Well."

Donna returned, holding a file. "Oi, you lot. All your storm troopers and your sonics. You're rubbish. Should've come with me."

"Why, where have you been?"

"Personnel." Caroline nodded. It was a good idea. "That's where the weird stuff's happening, in the paperwork. Because I spent years working as a temp, I can find my way round an office blindfold, and the first thing I noticed is an empty file."

"Why, what's inside it? Or what's not inside it?"

Donna showed them the label. "Sick days. There aren't any. Hundreds of people working here and no one's sick. Not one hangover, man flu, sneaky little shopping trip, nothing. Not ever. They don't get ill."

Mace frowned. "That can't be right."

"You've been checking out the building. Should've been checking out the workforce."

Martha laughed. "I can see why he likes you." She glanced at Caroline too, who then felt extremely uncomfortable.

Donna nodded. "Mmm hmm."

"You are good."

"Super temp."

"Dr. Jones, set up a medical post. Start examining the workers. I'll get them sent through."

"Come on, Donna. Give me a hand." Martha was about to leave, and then her gaze fell on Caroline, who was blushing by then. "Caroline?"

The three of them left, and Caroline found herself wishing she'd gone with the Doctor. But even she could tell that Martha wanted to talk to them, as companions, about something important. Besides, the Doctor would tell her everything, she knew he would.

And it would be good for her, it would be, to get to speak with one of the Doctor's old companions. The only problem was that Caroline could tell that, while it was quite obvious why Donna was with the Doctor, Martha was still curious about why Caroline was there.

They went to the personal office, since no one had been there anyways, and Martha began clearing a space for herself. "Do you think I should warn my mum about the ATMOS in her car?" Caroline was glad when she also looked at her for clarification, like she valued her opinion alongside Martha, a specially trained UNIT soldier.

Martha shrugged. "Better safe than sorry."

"I'll give her a call."

"Donna." Donna, who had been looking down at something, looked up. "Do they know where you are? Your family. I mean, that you're travelling with the Doctor?"

She frowned. "Not really. Although my granddad sort of waved us off. I didn't have time to explain."

"You just left him behind?"

"Yeah."

Martha nodded. "I didn't tell my family. I kept it all so secret, and it almost destroyed them."

"In what way?"

"They ended up imprisoned. They were tortured. My mum, my dad, my sister. It wasn't the Doctor's fault, but you need to be careful. Because you know the Doctor. He's wonderful, he's brilliant, but he's like fire. Stand too close and people get burnt." Then Martha turned to Caroline, who had been standing against one of the shelves of folders. "And you? Does your family know?"

Caroline swallowed. "I don't have any family." Both Martha and Donna frowned. "They died. My parents." She coughed. "Car accident. They were against ATMOS."

"I'm sorry."

"It's fine." She nodded. "None of my friends live in places suitable for personal cars, by the way."

"Do they know?"

"They only really cared about me because I saw them every day." It was true. Caroline had been forced to take a few jobs over the years, even if her parents had paid for her house. Each place she'd found a group of people who welcomed a quiet person to talk to, to drag around when they needed another person. All of them forgot her the moment she went somewhere else.

"Be careful, Caroline. Don't get attached to the Doctor. He's broken more hearts then he has ever realized."

Caroline was quiet then, as Donna helped Martha work. She just sort of snuck into the corner, her arms wrapped around herself. Martha was warning her against getting attached to him, against falling in love with him. And she'd never…she'd never thought about that.

The Doctor was wonderful and brilliant and he was helping Caroline express herself. But he was also a time traveling alien who dragged them into danger with a grin on his face.

Perhaps she should be more careful with her heart.

|C-S|

Donna and Caroline left Martha to continue checking the workers, instead going to find wherever the Doctor had gone off to. Caroline watched Donna carefully as they walked. While she had no one to warn, really, especially since the majority of the people she'd known from Adipose were currently in another country, there'd been a message on her phone when they'd landed back on Earth. But Donna, Donna had a family.

"I'm going to go home."

Caroline nodded. "For good or…"

Donna smiled. "Just to visit. I…feel bad about just abandoning them, leaving them with nothing. I owe it to at least tell them something." They spotted the Doctor then, who was standing on his own with Mace just walking away. "Doctor."

He spun around, grinning. "Oh, just in time. Come on, come on," he grabbed both of their hands, "we're going to the country. Fresh air and geniuses, what more could you ask?"

Donna made them stop. "I'm not coming with you. I've been thinking. I'm sorry. I'm going home."

The Doctor's eyes widened. He was still holding onto Caroline's hand, having let go of Donna's in order to face her. "Really?"

Donna nodded. "I've got to."

"Oh, if that's what you want. I mean, it's a bit soon. I had so many places I had wanted to take you. The Fifteenth Broken Moon of the Medusa Cascade, the Lightning Skies of Cotter Palluni's World, Diamond Coral Reefs of Kataa Flo Ko." He smiled, sighing. "Thank you. Thank you, Donna Noble, it's been brilliant. You've, you've saved my life in so many ways. You're-" Caroline laughed as he realized "you're just popping home for a visit, that's what you mean."

Donna smirked. "You dumbo."

The Doctor nodded. "And then you're coming back."

"Know what you are? A great big outer space dunce."

He laughed, rubbing his face. "Yeah." He looked towards Caroline, still holding her hand. "Did you know?"

She shrugged. "Now you really are going to have to take us there."

"Ready when you are, sir," a nearby soldier said.

"What's more, you can give me a lift." Donna pulled him by his arm into the jeep. "Come on. Broken moon of what?"

"I know, I know." They all squeezed into the jeep, though Caroline did end up having to partially sit on top of the Doctor in order for them all to fit.

Donna spent much of the ride warning Caroline about sitting there too long, otherwise the stick of a man would slice her in half.

The Doctor just grumbled.

When the jeep pulled up at Donna's street, both the Doctor and Caroline had to get out for her to as well. "I'll walk the rest of the way," she said, waving. "I'll see you back at the factory, yeah?"

Caroline got to sit in the middle this time, which was much less blush inducing then practically the Doctor's lap. "Bye!" The Doctor called as he closed the door again.

"And you be careful!"

A/N: Caroline's getting a bit more talkative, thankfully, but Martha's warning has made quite an impression on her. I wonder how she'll react to the events of these episodes.