Selfish

Caroline nodded at him. "Yours?" The Doctor grinned.

The crowd traveled back out to the ATMOS factory. It appeared like most of UNIT had gathered together, all of them wearing gasmasks.

"Latest firing stock," Mace said as he walked over, holding out some sort of gun for them to see. "What do you think, Doctor?"

"Are you my mummy?" Caroline stared at the Doctor until he winked at her.

Mace sighed. "If you could concentrate. Bullets with a rad-steel coating. No copper surface. Should overcome the cordolaine signal."

Caroline frowned. "The Sontarans have lasers and it's extremely difficult to see in this fog."

The Doctor nodded. "The night vision doesn't work."

"Thank you, Doctor, Caroline." He glanced at Caroline, and she had the impression that he had almost forgotten she was still there. "Thank you for your lack of faith. But this time, I'm not listening." He removed his gasmask and turned to the gathered soldiers. "Attention, all troops. The Sontarans might think of us as primitive, as does every passing species with an axe to grind. They make a mockery of our weapons, our soldiers, our ideals. But no more! From this point on, it stops. From this point on, the people of Earth fight back, and we show them! We show the warriors of Sontar what the human race can do. Trap One to Hawk Major! Go, go, go!"

There was a sudden massive downdraft, making Caroline stumble slightly from the force. The Doctor was quick to grab her arms and help keep her in place, the pair of them looking up at the large ship that was lowering itself, blowing away all of the gas.

"It's working!" Mace shouted over the winds. "The area's clearing. Engines to maximum."

"It's the Valiant," the Doctor grimaced and his grip on Caroline's arms tightened.

"UNIT Carrier Ship Valiant reporting for duty, Doctor. With engines strong enough to clear away the fog."

Everyone was finally able to pull off their masks, the air perfectly clear, at least in this space. It was true, the Valiant had blown away the gas here, but there was no saying what had happened elsewhere. The rest of the world was still slowly chocking.

"Whoa," the Doctor nodded, finally letting go of Caroline's arms, "that's brilliant."

"Getting a taste for it, Doctor?" Mace chuckled.

He shook his head and grabbed Caroline's hand again. "No, not at all. Not me." The Valiant must have meant something to him, he wouldn't have reacted this way to a simple ship. Some sort of memory, some sort of trauma.

"Valiant, fire at will."

Six green lasers shot out from the Valiant and converged on the ATMOS factory while UNIT soldiers used rocket launchers on the ground. The reaction was quick and it seemed like the Sontarans were overpowered, giving UNIT access to the factory once again.

Mace led the way down a hall way. "East and north secure. Doctor?" However, when he turned around, he found the trio hurrying down another corridor, the Doctor pulling out Caroline's phone again.

"Donna, hold on. We're coming."

'Martha' frowned at them, following a little ways behind because the Doctor was still holding onto Caroline's hand. "Shouldn't we follow the Colonel?"

He pulled out his sonic, scanning the area as they walked. "Nah, you and me, Caroline Attwater, Martha Jones. Just like old times." Technically, the old times were only with the actual Martha. But Caroline was still there now, still holding his hand, and he was never going to forget her. "Alien technology, this-a way."

They went down a few stairs until they reached the basement, lights flickering on with their arrival. "No Sontarans down here," the Doctor nodded. "They can't resist a battle. Here we go." He pushed open the door of a dimly lit laboratory, gazes immediately landing on the real Martha. She was strapped to a metal rack, asleep. "Oh, Martha, I'm so sorry." He checked her pulse, Caroline attempting to judge how tightly she was actually secured. "Still alive."

Martha's clone cocked a gun at them, though it was more directly at the Doctor's head.

"Am I supposed to be impressed?" he asked, not reacting. Caroline tried to emanate him, though she was finding it a bit more difficult.

"Wish you carried a gun now?"

He shook his head. "Not at all."

"I've been stopping the nuclear launch all this time."

"Doing exactly what I wanted. I needed to stop the missiles, just as much as the Sontarans. I'm not having Earth start an interstellar war. You're a triple agent."

Martha's clone frowned, irritated. "When did you know?"

The Doctor stood and walked around 'Martha'. "About you? Oh, right from the start. Reduced iris contraction, slight thinning of the hair follicles on the left temple." He pointed towards Caroline.

"Your reaction to family," she offered.

The Doctor nodded. "And, frankly, you smell. You might as well have worn a t-shirt saying clone. Although, maybe not in front of Captain Jack. I'll tell you about him soon, Caroline...actually, maybe not. You remember him, don't you? Because you've got all her memories. That's why the Sontarans had to protect her, to keep you inside UNIT. Martha Jones is keeping you alive." He had returned to the actual Martha and, in one smooth motion, pulled the device off of her head.

The clone collapsed as Martha jolted awake, screaming. Caroline ran for the gun as the Doctor comforted Martha, freeing her from the chair. "It's all right, it's all right, I'm here, I'm here. I've got you, I've got you."

"There was this thing, Doctor, this alien, with this head…" Martha spoke quickly, still slightly disoriented.

Her mobile rang.

"Oh! Blimey, I'm busy. Got it?" Caroline hurried over as Donna spoke.

"Yes. Now hurry up."

"Take off the covering. All the blue switches inside flick them up like a fuse box, and that should get the teleport working."

Martha stared over their shoulders at the clone, who was stirring. "Oh, my God. That's me."

The Doctor pulled off his coat and handed it to Martha, who'd been forced into some sort of medical gown. Together, with Caroline, they went over to the teleport to begin fixing it from this end, though it was the Doctor doing most of the work. Martha, in turn, went to sit by the clone.

"Don't touch me." The clone flinched away as Martha reached out. The Doctor very quickly explained part of his plan to Caroline, as well as a little bit more about how the teleport worked.

"It's not my fault. The Sontarans created you, but you had all my memories."

"You've got a brother, sister, mother and father."

"If you don't help me, they're going to die."

"You love them."

"Yes. Remember that?"

"The gas," the Doctor called over. "Tell us about the gas." They could just barely hear the conversation the two women were having.

"He's the enemy," the clone spat.

"Then tell me. It's not just poison, what's it for? Martha, please."

The clone hesitated. "Caesofine concentrate. It's one part of Bosteen, two parts Probic five."

The Doctor straightened, stepping out of the teleport. "Clonefeed. It's clonefeed!"

"What's clonefeed?" Martha asked, frowning.

"Like amniotic fluid for Sontarans. That's why they're not invading. They're converting the atmosphere, changing the planet into a clone world. Earth becomes a great big hatchery. Because the Sontarans are clones, that's how they reproduce. Give them a planet this big, they'll create billions of new soldiers. The gas isn't poison, it's food!" The Doctor ran back into the teleport, needing to hurry now.

The clone winced. "My heart. It's getting slower."

"There's nothing I can do."

"In your mind, you've got so many plans. There's so much that you want to do."

Martha nodded. "And I will. Never do tomorrow what you can do today, my mum says, because-"

"Because you never know how long you've got. Martha Jones…all that life…" she exhaled and the clone was dead. Martha took her engagement ring back while Caroline grabbed the phone, hearing Donna shout something.

"Doctor! Blue switches done, but they've found me!"

The Doctor jumped out of the teleport, flashing his sonic at it. "Now!" Donna appeared on the pad, looking terrified, before running forwards and hugging the Doctor.

"Have I ever told you how much I hate you?"

"Hold on, hold on. Get off me, get off me." Donna just turned to hug Caroline instead. "Got to bring the TARDIS down." He soniced the controls again. "Right, now. Martha, you coming?"

Martha looked down at the phone the clone had been carrying, a simple yes or no question about the launch team displayed. "What about this nuclear launch thing?"

He shrugged. "Just keep pressing N. We want to keep those missiles on the ground."

Donna wasn't that surprised to see Martha there, but she was to see the clone behind her. "There's two of them."

Caroline nodded. "Quite a long story."

"Here we go." The Doctor grinned, motioning for all of them to join him inside the teleport. "The old team, back together. Well, the new team."

"We're not going back on that ship!"

The Doctor shook his head. "No, no, no. No. I needed to get the teleport working so we could get to…" they teleported back to Rattigan Academy "…here! The Rattigan Academy, owned by…" he reached out a hand to stop Caroline, who had ended up standing behind him, from stepping forward as Luke pointed a gun at them.

"Don't tell anyone what I did! It wasn't my fault, the Sontarans lied to me, they…"

The Doctor stormed forward and grabbed the gun from him, throwing it away, before stalking out of the room. The three companions hurried after him. "If I see one more gun…"

Donna glanced at Martha, who was still wearing the Doctor's coat. "You know, that coat sort of works."

Martha laughed, blushing. "I feel like a kid in my dad's clothes."

"Oh well, if you're calling him dad, you're definitely getting over him."

Caroline rushed forward to the Doctor, who was running around the lab from before. He appeared to be grabbing components from random devices that Luke's students had left behind, combining them. Once he spotted her, he just pointed at a few objects and she grabbed them for him.

"That's why the Sontarans had to stop the missiles," he explained as he worked. "They were holding back. Because caesofine gas is volatile, that's why they had to use you to stop the nuclear attack. Ground-to-air engagement could spark off the whole thing."

Caroline frowned. "They want to set fire to the atmosphere?"

"Yeah," the Doctor nodded. "They need all the gas intact to breed their clone army. And all the time we had Luke here in his dream factory. Planning a little trip, were we?"

"They promised me a new world," Luke mumbled, looking away.

"You were building equipment, ready to terraform El Mondo Luko so that humans could live there and breathe air with this." He looked at the device he'd built. "An atmospheric converter."

A second later, he had grabbed it and they were running back outside. Now, they couldn't even see London, it was covered in such thick fog. Caroline didn't know if she knew anyone in London at the moment, all the friends she knew about were out of the country. But Donna and Martha's families were there, chocking, most of Earth was chocking.

"That's London," Donna breathed, staring out at it while the Doctor fidgeted with the converter. "You can't even see it. My family's in there."

"If I can get this on the right setting…" he mumbled.

Martha stepped forward, frowning. "Doctor, hold on. You said the atmosphere would ignite."

He grinned. "Yeah, I did, didn't I?"

He pressed a button and a burst of flame shot up into the sky. The gas ignited and spread, burning through the clouds and revealing a brilliantly blue sky. Earth had been saved.

"He's a genius," Luke laughed.

"Just brilliant."

The Doctor was grinning, confident, and Caroline was laughing. But then his face fell, eyes hardening, and Caroline was horribly worried.

"Now we're in trouble." He grabbed the converter again and ran back into the building, Caroline only a step behind. It was clear he was returning to the teleport, and she stopped a second before he had stepped inside, sonicing it on the way.

"Right, so…" he swallowed and Caroline knew that expression. "Donna, thank you for everything. Martha, you too. Oh, so many times. Caroline, it has been my pleasure. Luke," he sighed, "do something clever with your life."

Caroline was staring with her eyes wide. He couldn't, he wouldn't. They'd only just started, he'd only just begun to show her the universe. "You're saying goodbye." As had become tradition, Donna spoke what Caroline was thinking.

"Sontarans are never defeated. They'll be getting ready for war. And, well, you know," he looked down, "I've recalibrated this for Sontaran air, so…"

She stepped back, standing alongside Martha and Donna. "You're going to ignite them."

Donna nodded. "You'll kill yourself."

"Just send that thing up on its own," Martha tried. "I don't know. Put it on a delay."

"I can't…"

"Why not?"

He sighed. "I've got to give them a choice." And then he teleported away.

Caroline clutched her mouth, all three of the companions suffering from the fact the Doctor was sacrificing himself in order to offer the Sontarans, who most likely wouldn't care, the chance to survive.

"I hate that man," Martha whispered. They stared at the teleport, wishing that the Doctor would reappear, reveal some convoluted plan that would result in his safety. Because Caroline didn't know what she would do. It had hardly been any time, but his world was already so wonderfully different and dangerous.

And he made her feel so impossibly loved.

Luke rushed forwards, messing with some of the controls.

"What are you doing?"

"Something clever." And then he had teleported away too, up to the Sontaran ship.

The Doctor reappeared a second later, falling to the ground struggling for breath. It only took his companions a few seconds before they rushed forward to help him stand. And for Donna and Martha to slap him.

|C-S|

The Doctor found Caroline sitting on the steps of the TARDIS. Donna was checking on her family, Martha was ensuring UNIT was still functioning properly, but Caroline had no one to check on.

"How are you?"

She picked at a loose threat in the sleeve of her sweater. "You were going to sacrifice yourself. To save the Sontarans."

"They deserved it."

"This wasn't a fixed event, then." Caroline looked up.

"That was different-"

"I know." She nodded. "Pompeii was a fixed event. You had to, you had no choice. But, if you were willing to change things here, if you were willing to alter the course of events, one can assume that means they weren't fixed. Which meant everything you did was completely your choice. You were going to sacrifice yourself because you wanted to."

He'd done it again. He'd done the dangerous thing. He'd picked up the person with barely any connections, with a bursting desire for adventure that would never be silenced, not even when he abandoned them. He'd chosen someone who wanted to travel and had no life to return to when he was finally forced to leave them.

And he'd always gotten attached. He'd always found love, or friendship. And then he'd have to leave them, because that was too dangerous. Because they were human and he was a Time Lord and he'd keep living and they'd die. And he'd just end up with broken hearts, again.

If he was clever, he'd leave them. He'd never even pick anyone in the first place. He'd just be a lonely man traveling in the universe.

But, most of the time, he wasn't a clever man. Most of the time, he was a very stupid and a very selfish man.

"I'm sorry."

"Good."

He held out a hand, not certain what he was hoping for. "Want to come see how Donna is?" Would she want to be left at home? Would he be alone again, abandoned in the universe? It seemed to be his destiny, and maybe that's why he was refusing. He had never been good at listening to people who tried to dictate what he did with his future.

They retrieved Martha first. She wanted to say goodbye to Donna before leaving, for good. And the Doctor understood that, he did. He knew that's what would happen to most people he left, in the end. They would rebuild their lives using what he'd taught them, protect the Earth. Become stronger.

But they had to suffer to do that. They had to readjust to a life without aliens and running and traveling through time. They had to relearn how to be human and normal again. How to bounce back after he'd ruined them.

Next they hunted down Donna.

"How were they?" Martha asked her.

Donna smiled, shrugging. "Oh, same old stuff. They're fine." She walked up to stand by the console next to all of them. "So, you going to come with us? We're not exactly short of space." Caroline giggled.

"Oh, I have missed all this, but, you know." Martha looked around them, nodding. "I'm good here, back at home. And I'm better for having been away. Besides," she held up her engagement ring, "someone needs me. Never mind the universe, I've got a great big world of my own now." She walked towards the open doors, laughing.

Only for them to slam shut and the TARDIS to activate on its own accord, sending them all flying. Everyone clung to some different object, trying to gain traction as the TARDIS flung them through the universe.

"What?" the Doctor shouted. "What?"

"Doctor, don't you dare!" Martha managed to glare at him.

"No, no, no!" he tried to pull himself closer to the controls. "I didn't touch anything. We're in flight. It's not me."

"Where are we going?" Donna asked. Caroline would have said something, but she was already trying to determine how dangerous something that could hijack the TARDIS could be.

"I don't know. It's out of control!"

Martha shook her head. "Doctor, just listen to me. You take me home. Take me home right now!"

But the Doctor couldn't do anything, not anymore, not while the TARDIS flew through the Universe to some point not even he could determine.

A/N: Caroline's not that happy with the fact the Doctor was willing to sacrifice himself, but she's made the Doctor think. I always felt like the 10th Doctor, in particular, was someone who thought about the fact he would have to leave companions behind eventually, so I wanted to include that in this story :)