"He's going to choke," Donna gasped through her tears. "Doctor!"

Jessie shook her head before ducking inside of the car, phasing through. She began coughing on the gas a little as her Time Lord side fought her Asgardian side to be fine with the gas, and she grabbed Wilf and pulled her out with him. She stumbled a little away from the car as Sylvia grabbed Wilf. "Thanks," Wilf wheezed.

"Yeah," Jessie panted as the Doctor took her in his arms, checking her over. "Cheers, soldier."

"Get inside the house," the Doctor told them. "Just try and close off the doors and windows."

"Doctor!" Steve's voice shouted as a black cab pulled up, Ross at the wheel.

"This is all we could find that hasn't got ATMOS," Ross reported.

The Doctor turned to Donna. "Donna, you coming?" he asked.

Donna swallowed. "Yeah," she replied with a nod.

"Donna," Sylvia pleaded. "Don't go. Look what happens every time that Doctor and Bad Wolf appears! Stay with us, please!"

"You go, my darling," Wilf told her.

"Dad!" Sylvia gasped.

"Don't listen to her," Wilf told her. "You go with those two. That's my girl."

Donna nodded, crying a little as she got into the car with the two Time Lords.

***

"Ross, Steve, look after yourselves," the Doctor told them as they got out of the cab. "Get inside the building."

"Will do," Ross replied as the three of them ran inside.

"The air is disgusting," Donna coughed.

"It's not so bad for me," the Doctor said with a shrug. "Go on. Inside the TARDIS." He stopped. "Oh, I've never given you a key." He pulled it out of his coat pocket and handed it to her. "Keep that. Go on, that's yours. Quite a big moment, really."

"Yeah, maybe we can get sentimental after the world's finished choking to death," Donna commented.

He winced. "Good idea."

"Where are you going?"

"To stop a war!" he replied, and he and Jessie ran at full speed towards the ATMOS complex.

***

The Doctor separated from Jessie as she went down to check on the UNIT soldiers in the complex as he headed back to the command center. "Right, then! Here I am!" he declared. "Good." He pointed at Mace. "Whatever you do, Colonel Mace, do not engage the Sontarans in battle. There is nothing they like better than a war. Just leave this to me."

"And what are you going to do?" the Colonel asked.

"I've got the TARDIS," the Doctor replied. "I'm going to get onboard their ship." He looked over at Martha, trying not to cringe at how obvious it was that she was . . . different. "Come on."

She stood and followed him as they headed for the TARDIS, and he blinked when he saw the TARDIS was completely gone. "What?!"

"But where's the TARDIS?" Martha asked, looking around.

"Taste that, in the air," the Doctor replied, flicking his tongue out and grimacing. "Yuck. That sort of metal tang. Teleport exchange. It's the Sontarans. They've taken it. I'm stuck on Earth like . . . like an ordinary person. Like a human. How rubbish is that?" He nodded at her. "Sorry. No offense, but come on."

"So what do we do?" Martha asked.

"Well, I mean, it's shielded. They could never detect it."

"What?"

He eyed her. "I'm just wondering, have you phoned your family and Tom?"

"No. What for?"

He raised an eyebrow at her. "It's definitely not Martha," he called out to Jessie. "The gas," the Doctor said out loud. "Tell them to stay inside."

"'Course I will," Martha laughed. "Yeah, but what about Donna? I mean, where's she?"

"Oh, she's gone home," the Doctor replied casually. "She's not like you. She's not a soldier." He turned. "Right. So! Avanti!"

***

"Change of plan," the Doctor said as they made it to the mobile command center, Jessie back inside, hair pulled up in a ponytail and dressed in full SHIELD attire.

"Good to have you fighting alongside us, Doctor," Mace told him.

"I'm not fighting," the Doctor told him. "I'm not-fighting as in not hyphen fighting, got it? Now does anyone know what this gas is yet?"

"We're working on it," Martha replied.

"It's harmful, but not lethal until it reaches eighty percent density," a blonde-haired woman replied. "We're having the first reports of deaths from the center of Tokyo City."

"And who are you?" the Doctor asked.

"Captain Marion Price, sir," she replied, saluting.

"Oh, put your hand down!" the Doctor groaned. "Don't salute!"

"Jodrell Bank's traced a signal, Doctor, coming from five thousand miles above the Earth. We're guessing that's what triggered the cars."

"The Sontaran ship," Jessie guessed.

"NATO has gone to Defcon One," Mace told them. "We're preparing a strike."

"You can't do that!" the Doctor protested. "Nuclear missiles won't even scratch the surface! Let us talk to the Sontarans."

"You're not authorized to speak on behalf of the Earth."

Jessie snorted. "I think he earned that right a long time ago." She stuck her sonic in the communications system. "Calling the Sontaran Command Ship under Jurisdiction Two of the Intergalactic Rules of Engagement, this is the Bad Wolf!"

The screen flickered on with an image of the Sontarans, but something else caught Jessie's eye. Her eyes widened when she swore she saw a flickering image of Saleen Harper shouting her name through one of the monitors, and she quickly moved over, doing a scan, blinking back tears when she realized she must have seen it.

"Bad Wolf," Staal greeted them. "Doctor. Breathing your last?"

"My God, they're like trolls," Mace breathed.

"Yeah, loving the diplomacy, thanks," the Doctor said sarcastically. "So, tell me, General Staal. Since when did you lot become cowards?"

"How dare you!" Staal shouted.

"Oh, that's diplomacy?" Mace asked with a snort.

"It's better than what he did a good few years ago," Jessie chuckled. "Back then, his only way of communication was waving a bomb in your face, followed by blowing stuff up. He gets an A plus in the diplomacy area right now."

"Doctor, you impugn my honor," Staal declared.

"Yeah, I'm really glad you didn't say belittle, because then I'd have a field day," the Doctor snorted. "But poison gas? That's the weapon of a coward, and you know it. Staal, you could blast this planet out of the sky, and you're sitting up above watching it die. Where's the fight in that? Where's the honor?"

"Or," Jessie began, "are you lot planning something else? Because this isn't normal Sontaran warfare. What're you all up to?"

"A general would be unwise to reveal his strategy to the opposing forces," Staal shot down.

"So maybe the war's not going so well, then," Jessie said, plopping down in a chair and swinging her feet up so they were on the desk in front of her. "Losing, are we?"

"Such a suggestion is impossible!" Staal shouted at her.

"What war?" Mace asked.

"The war between the Sontarans and the Rutans," the Doctor explained. "It's been raging far out in the stars for fifty thousand years. Fifty thousand years of bloodshed, and for what?"

"For victory," Staal replied. "Sontar-ha! Sontar-ha!"

The rest of the Sontarans around him began chanting it, and the Doctor rolled his eyes. "Give me a break," he muttered, sonicking the channels to change.

For a split second, Jessie saw another monitor flicker, this time with Jake Simmonds of all people shouting for the Doctor, before she blinked, and it was gone. She shook her head, pinching the bridge of her nose. "Doctor, I would seriously recommend that this dialogue is handled by official Earth representation," Mace tried again.

"Your recommendation has been noted," Jessie told him. "And denied."

The Doctor turned the Sontarans back on. "Finished?" he asked casually.

"You will not be so quick to ridicule when you'll see our prize," Staal told him. "Behold." He held out an arm, and Jessie stiffened at the sight of the TARDIS. "We are the first Sontarans in history to capture a TARDIS!"

"Well, as prizes go, that's noble," the Doctor commented, stressing noble. "As they say in Latin, Donna nobis pacem. Did you never wonder about its design? It's a phone box. It contains a phone. A telephonic device for communication. Sort of symbolic. Like if only we could communicate, you and I."

"All you have communicated is your distress, Doctor."

"Big mistake, though, showing it to me." He raised an eyebrow. "Because I've got remote control."

"Cease transmission!" Staal ordered.

"Liar," Jessie sang as the screen went blank, and she pointed her sonic at the Doctor. "Liar, liar."

"Ah, well," he sighed.

"That achieved nothing!" Mace spat.

"Oh, you'd be surprised," the Doctor snorted.

***

Donna sat in the TARDIS, tossing the phone the Bad Wolf had left on the console from hand to hand before swallowing and dialing a familiar number. She held it up to her ear when she heard the line pick up. "Mum," she said, swallowing. "You all right?"

"Donna," Sylvia replied. "Where are you, sweetheart?"

"Is that her?" Wilf asked dimly.

"Oh, just finish the job!" Sylvia told him. "Your granddad's sealing us in. He's sealing the windows. Our own house, and we're sealed in. All those things they said about pollution and ozone and carbon, they're really happening, aren't they?"

"There's people working on it, Mum," Donna told her. "They're going to fix it. I promise."

"Oh, like you'd know," Sylvia snorted. "You're so clever."

"Oh, don't start," Donna whispered. "Please don't."

"I'm sorry," Sylvia apologized. "I wish you were here."

"Now, come on, Sylvia," Wilf scorned. "Look, that doesn't help. Donna, where are you?"

Donna looked around. "It's . . . sort of hard to say," she replied. "You all right?"

"Yeah. Fighting fit, yeah. Are they with you? The Doctor and the Bad Wolf?"

"Oh, the Doctor and the Bad Wolf," Sylvia sighed.

"No," Donna replied in a whisper. "I'm all on my own."

"Look, you promised they were going to look after you!" Wilf told her.

"They will, Gramps," she assured him. "There's something he needs me to do. I just don't know what."

"Well, I mean, the whole place is covered. The whole of London, they're saying. The whole . . . the whole world! It's the scale of it, Donna. I mean, how can two people stop all that?"

"Trust me, they can do it."

"Yeah, well, if they don't, you tell them they'll have to answer to me."

Donna cracked a grin. "I will," she promised. "Just as soon as I see them, I'll tell them."

"Huh."

Donna sighed as the line was cut.

***

"There's carbon monoxide, hydrocarbons, nitrogen oxides, but ten percent unidentified," Martha reported as Jessie went back to check on the UNIT soldiers. "Some sort of artificial heavy element we can't trace. You ever seen anything like it?"

"It must be something the Sontarans invented," the Doctor muttered, looking it all over. "This isn't just poison. They need this gas for something else. What would that be?"

"Launch grid online and active," Price announced from her position.

"Positions, ladies and gentlemen," Mace called as the Doctor spun, looking at the map in horror. "Defcon One initiatives in progress."

"What?" the Doctor demanded. "I told you not to launch!"

"The gas is at sixty percent density," Mace told him. "Eighty percent, and people start dying, Doctor. We've got no choice."

"Launching in sixty," Price counted down. "Fifty nine, fifty eight, fifty seven, fifty six. Worldwide nuclear grid now coordinating. Fifty four, fifty three."

"You're making a mistake, Colonel," the Doctor warned. "For once, I hope the Sontarans are ahead of you."

"North America, online," Price reported. "United Kingdom, online. France, online. India, online. Pakistan, online. China, online. North Korea, online. All systems locked and coordinated. Launching in ten, nine, eight, seven, six, five . . . "

"God save us," Mace murmured.

"Four, three, two, one, zero."

And the screen went entirely blank. Out of the corner of his eye, the Doctor saw Martha slip her phone back in her pocket. "What is it?" Mace asked. "What happened? Did we launch? Well? Did we?"

"Negative, sir," Price breathed. "The launch codes have been wiped, sir. It must be the Sontarans."

"Can we override it?"

"Trying it now, sir."

"Missiles wouldn't even dent that ship, so why are the Sontarans so keen to stop you?" the Doctor asked, turning to Martha. "Any ideas?"

"How should I know?" she asked with an attitude.

Oh, you're definitely not Martha Jones.

***

"Still stinking out there?" Jessie joked as she joined the UNIT soldiers.

"It's stinking out there," Ross confirmed.

Steve frowned. "Hold on a minute." He held up a finger, and everyone quieted around them, and Jessie could hear it, too. The stomp of boots. "Enemy within," he said.

Jessie quickly gestured everyone down, pulling her gun and setting it onto the kill setting as Sontarans marched around the corner. "Enemy within!" Ross snapped into his walkie-talkie. "At arms!" The UNIT soldiers raised their own guns. "Greyhound Forty declaring absolute emergency. Sontarans within factory grounds. East corridor, grid six!"

"Absolute emergency!" Mace replied. "Declaring Code Red! All troops, Code Red!"

"Get out of there!" the Doctor shouted. "Jess, get out of there!"

Jessie swallowed. "I'm not going anywhere."

"All troops, open fire!" Mace ordered.

Jessie started firing immediately, the advancements on hers taking out a few of the Sontarans, but as the Sontarans returned fire, more troops fell among them. "Doctor, it's the cordolaine signal," she said tightly.

"Guns aren't working," Ross reported. "Inform all troops, standard weapons do not work!"

"Run!" Jessie shouted, grabbing Ross's arm and Steve's, and they ran around the corner, heading for the stairwell to make it back to HQ.

***

"Greyhound Forty, report. Over," Mace ordered into his walkie-talkie. "Greyhound Forty, report. Greyhound Forty, report!"

"Greyhound Forty, taken over," Jessie's voice came over, and the Doctor slumped in relief. "I thought he specifically told you not to try and attack!"

"We're on our way up," Steve's voice cut in. "But they've taken the entire factory."

"Why?" the Doctor asked, pacing. "They don't need it! Why attack now? What are they up to? Times like this, I could do with the Brigadier. Or maybe even the SHIELD team." He eyed Mace. "No offense."

"None taken," Mace replied easily. "Sir Alistair's a fine man, if not the best. Unfortunately, he's stranded in Peru."

There was a warping sound, and Jessie burst in, tugging Steve and Ross in with her. Her hair was a mess, and Steve and Ross were sweating horribly, and all three of them were panting. "They're getting massacred!" Jessie shouted at Mace as she marched up to him, eyes glowing with the Aether. "Why don't you ever listen?!"

"Launch grid back online," Price said tensely. And the screen went blank again. "They're inside the system," she reported. "It's coming from within UNIT itself."

"Trace it," Mace ordered, stepping away from Jessie. She moved after him, but the Doctor grabbed her and pulled her tightly to him. "Find out where it's coming from, and quickly. Gas levels?"

"Sixty six percent in major population areas, and rising," she replied.

Mace led them inside of his office. "Why are they defending the factory only after we were inside?" Mace asked.

"Because they wanted UNIT here," the Doctor guessed. "You gave them something they needed. Something now hidden inside the factory. Something precious."

"We've got to recover it," Mace decided. "This cordolaine signal thing. How does it work?"

"It's the bullets. It causes expansion of the copper shell."

"Excellent. I'm on it."

"For the billionth time, you can't fight Sontarans!" the Doctor growled, but Mace ignored him. The Doctor shook his head, then turned to Jessie. "Phone," he whispered.

She nodded and handed it to him, and he dialed Martha's cell. "What's happened?" Donna asked as she answered. "Where are you?"

"Still on Earth," the Doctor replied. "But don't worry. We've got our secret weapon."

"What's that?"

"You."

"Oh. Somehow, that's not making me happy. Can't you just zap us down to Earth with that remote thing?"

"He's a liar about that," Jessie told her.

"Yeah, I haven't got a remote," the Doctor admitted with a wince. "Though I really should. I need you on that ship. That's why I made them move the TARDIS. I'm sorry, but you've got to go outside."

"But there's Sonteruns out there!"

"Sontarans," Jessie corrected.

"But they'll all be on battle stations right now," the Doctor told her. "They don't exactly walk about having coffee. I can talk you through it."

"But what if they find me?"

"I know, and I wouldn't ask, but there's nothing else I can do. The whole planet is choking, Donna."

She paused. "What do you need me to do?"

Jessie smiled. "Atta girl, Super Temp!"

"The Sontarans are inside the factory, which means they've got a teleport link with the ship, but they'll have deadlocked it. I need you to reopen the link."

"But I can't even mend a fuse!"

"Donna, stop talking about yourself like that," Jessie ordered. "You can do this. I promise."

There was a pause, then Donna whispered, "There's a Sonterun." Pause. "Sontaran."

"Did he see you?" the Doctor asked.

"No, he's got his back to me."

"Right. Donna, listen. On the back of his neck, on his collar, there's a sort of plug, like a hole. The Probic vent. One blow to the Probic vent knocks them out."

"But he's going to kill me!"

"Donna, you've got to try," Jessie pleaded.

There was some shuffling around, then a banging sound, and Donna gleefully reported, "Back of the neck!"

"Now, then, you got to find the external junction feed to the teleport," the Doctor continued.

"What? What's it look like?"

"A circular panel on the wall. big symbol on the front, like a . . . like a letter T with a horizontal line through it. Or . . . or two Fs back to back."

"Oh. Well, there's a door."

"Should be a switch by the side."

"Yeah, there is, but it's Sontaran shaped. You need three fingers."

"Live long and prosper?" Jessie offered.

"Oh, yeah," Donna chuckled. "I'm through."

"Oh, you are brilliant, you are," the Doctor said fondly.

"Shut up. Right. T with a line through it."

"He's back," Steve warned.

"Gotta go," Jessie told her. "Keep the line open."

The Doctor slipped his phone into his pocket as Mace joined them. "Counter attack," he told them.

"We said you don't stand a chance!" the Doctor snapped.

Jessie caught a gas mask thrown at her, and she eyed it funnily before checking herself over. "I'm pretty sure I didn't put on a British flag shirt . . . "

"You're not going without me," Martha stated.

The Doctor and Jessie exchanged glances. "Wouldn't dream of it," the Doctor finally said as they followed Mace out.

***

"Latest firing stock," Mace told them when they were outside with the gas masks on. "What do you think, Doctor?"

"Are you my mummy?" he replied with a rather good impression of the child.

Jessie giggled. "What, no barrage balloon this time?"

"No bananas, or Jack," the Doctor said, and they burst out laughing.

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

"But the Sontarans have got lasers," the Doctor pointed out. "You can't even see in this fog! The night vision doesn't work!"

"Thank you, Doctor. Thank you for your lack of faith. But this time, I'm not listening."

"He hasn't been listening from the gecko," Jessie muttered as he removed his gas mask to shout.

"Attention, all troops!" Mace called. "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." He lifted a walkie-talkie. "Trap One to Hawk Major. Go, go, go."

There was a massive wind blow, and the gas began to blow away. "Whoa!" Jessie gasped in amazement.

"It's working," Mace told them. "The area's clearing. Engines to maximum!"

"It's the Valiant!" the Doctor cheered as the massive ship dropped into view, its engines whirling around and around.

"UNIT Carrier Ship Valiant reporting for duty, Doctor," Mace told him with a smile. "With engines strong enough to clear away the fog."

"That really is clever," Jessie said as she pulled her gas mask off.

"Brilliant," the Doctor agreed.

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

"No, not at all," the Doctor replied.

"Valiant, fire at will," Mace ordered.

Six green lasers descended from the Valiant to form one, and it hit the ATMOS factory dead on. Jessie could see Steve lead the remaining UNIT soldiers in to face the Sontarans, and they all listened in on hearing reports being called out. "East and north secure," Mace told them. "Doctor? Bad Wolf?"

Mace headed off, and the Doctor pulled out Jessie's phone. "Donna, hold on," he told her. "We're coming."

"Shouldn't we follow the Colonel?" Martha asked.

"Nah," the Doctor replied, scanning the area with his sonic screwdriver, and raising an eyebrow when it didn't just pick up Martha Jones's signal. "The three of us, Martha Jones. Just like old times. Alien technology this-a way!"

Jessie ran after him as he led the way, and she saw Martha press something on her phone before she ran after them.

***

"Oh, the basement," Jessie sighed. "It's always the basements."

"No Sontarans down here," the Doctor told them. "They can't resist a battle." He stopped in front of a door. "Here we go."

They entered, and Jessie gasped and instantly ran towards Martha Jones, lying back in some kind of holster. "Martha!"

"Oh, Martha," the Doctor sighed. "I'm so sorry."

"She's still alive," she told him.

There was the click of a gun, and Jessie spun, drawing her own, but stopped when she saw the clone aiming a gun at the Doctor's head. The Doctor didn't even flinch. "Am I supposed to be impressed?" he asked mildly.

"Wish you carried a gun now?" the clone asked.

"Not at all."

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

"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."

The clone furrowed her eyebrows. "When did you know?"

"About you? Oh, right from the start," he snorted. "Reduced iris contraction, slight thinning of the hair follicles on the left temple. And frankly, you smell. You might as well have worn a T-shirt saying 'clone.' Although, maybe not in front of Captain Jack."

"You remember him, right?" Jessie asked. "Because you've got all of her memories. That's why the Sontarans had to protect her, to keep you inside UNIT. Martha's keeping you alive."

She took the headpiece off of Martha's head, and Martha gasped, waking up as the clone dropped to her knees, and the Doctor kicked the gun away. "It's all right," Jessie whispered, hugging Martha. "It's all right. We're here. We're here. I've got you, I've got you."

"There was this thing," Martha panted. "Doctor, this alien, with this head!"

Jessie's phone rang, and the Doctor rolled his eyes as Jessie came over. "Oh, blimey, we're busy," he whined as they put their heads together to listen. "Got it?"

"Yes," Donna hissed. "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."

"Oh, my God," Martha gasped. "That's me!"

"Yeah, long story," Jessie told her as the Doctor slipped his coat off and put it over Martha before running over to the matching teleport in the corner.

Martha headed towards her clone, but the clone backed away. "Don't touch me," she spat.

"It's not my fault," Martha told her duplicate. "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?"

"What about the gas?" Jessie asked. "Tell us about the gas."

"You're the enemy!" the clone snapped at her before wincing. "Both of them are!"

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

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

"Clonefeed!" the Doctor shouted, jumping up. "It's clonefeed!"

"What's clonefeed?" Martha asked.

"Like amniotic fluid for Sontarans," the Doctor explained. "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."

"My heart," the clone whispered. "It's getting slower."

"There's nothing I can do," Martha apologized.

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

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

"Because you never know how long you've got," the clone finished. "Martha Jones . . . all that . . . life . . . "

The clone slid to the ground, her eyes closing. Martha swallowed, then took back her engagement ring. "Doctor!" Donna called. "Blue switches done, but they've found me!"

"Now!" the Doctor shouted.

Jessie buzzed the teleport with her sonic screwdriver, and Donna appeared inside. "Have I ever told you how much I hate the two of you?" she growled before hugging them fiercely.

"Hold on! Hold on!" the Doctor protested, voice muffled. "Get off me, get off me!"

"I'll get the TARDIS back," Jessie chuckled, making a few adjustments.

"Right, now. Martha?" The Doctor turned to her. "You coming?"

"What about this nuclear launch thing?" Martha asked, holding up her phone.

"Just keep pressing N," the Doctor told her. "We want to keep those missiles on the ground."

"There's two of them," Donna whispered, seeing the clones.

"Long story," Jessie told her.

"Here we go!" the Doctor cheered, looking around. "The old team, back together! Well, the new team."

"We're not going back on that ship!" Donna protested as the two Time Lords got on the teleport, but Martha joined them, and Donna reluctantly did as well.

"No, no, no, no," the Doctor replied with a smirk. "I needed to get the teleport working so that we could get to - "

"Oh, great, back here," Jessie sighed as they appeared in the Rattigan Academy. "The Rattigan Academy, owned by - "

Luke had a gun aimed right in her face. "Don't tell anyone what I did," he ordered shakily. "It wasn't my fault! The Sontarans lied to me! They said - !"

The Doctor growled angrily, grabbing the gun and nearly ripping out Luke's arms as he wrenched it away. "If I see one more gun pointed at either one of us . . . " he threatened as he stalked towards the laboratory.

"You know," Donna said slowly to Martha, "that coat sort of works."

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

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

"He was never mine," Martha corrected with a wink at Jessie's. "She had him wrapped around her finger even when they hated each other."

"He's still whipped," Jessie said mildly as she followed her husband, and both of the women laughed as they followed.

***

"That's why the Sontarans had to launch the missiles," the Doctor said hurriedly as he worked on building something. "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."

"What, like set fire to the atmosphere?" Martha asked.

"Yeah," Jessie replied. "They need every last bit of the gas intact to breed their clone army. And all that time, Luke here was in his dream factory." She raised an eyebrow at Luke. "Planning a little trip, were we?"

"They promised me a new world," he told them.

"You were building equipment, ready to terraform El Mondo Luko so that humans could live there and breathe the air with this," the Doctor told him, holding up the gizmo he was building. "An atmospheric converter."

He ran out towards the front, and Jessie took off after him. They emerged on the front lawn, and Jessie's eyes widened at the mass of grey fog completely covering the area. "That's London," Donna whispered. "You can't even see it! My family's in there!"

"If I can get this on the right setting," the Doctor muttered, fiddling with the converter.

"You don't need it," Jessie told him.

He looked up at her, and his eyes darkened. "No," he said instantly.

"I can do it!" she argued. "And more importantly, you know that there's not a chance this could go wrong. This?" She pointed at the converter. "It could explode and take us all with it, knowing you."

He stared at her before looking over her shoulder. "You two?" he asked.

"Trust her with my life," Martha said truthfully.

Donna nodded. "Good enough for me, Spaceman."

The Doctor took a deep breath, then nodded, standing up and kissing her tightly. "Be careful."

"Hold on a minute," Martha spoke up as Jessie stepped up, clenching her fists and seeing the Aether swirl around them. "You said the atmosphere would ignite."

"Yeah," the Doctor replied, not taking his eyes off of Jessie. "I did, didn't I?"

Jessie flung her arms up in the air, and waves of fire and Aether shot up into the air. Donna let out a small scream, and the Doctor pulled her and Martha back. Jessie concentrated, sending the fire outwards, letting it flow through the entire atmosphere. The flames raced everywhere, covering the entire sky, and the Doctor laughed happily, and Martha began cheering. Jessie pulled her powers back, stumbling a little at the force of using so much, and the Doctor ran to her side, kissing her fiercely. She kissed him back, bringing her hand to the back of his neck to support herself, and then Martha was hugging her, and so was Donna, and she laughed, the four of them in a small circle hug of their own.

"But we're still not done," the Doctor told her.

Jessie squeezed her eyes shut. "I know," she admitted.

***

"Right," the Doctor said as they went back to the recreation room. "So. Donna, thank you for everything."

"Martha, thank you for giving back my life," Jessie told her, and both women stopped dead. "And Luke? You'd better do something clever with your life besides all of this."

"Your'e saying goodbye," Donna whispered.

"Sontarans are never defeated," the Doctor told them. "They'll be getting ready for war. And well, you know . . . " He waved the converter. "I've recalibrated this for Sontaran air, so - "

"You're going to ignite them!" Martha gasped.

"You'll kill yourself!" Donna added.

"Just send that thing up on its own! I don't know, put it on a delay!"

"I can't," the Doctor apologized.

"Why not?" Donna asked.

"We have to give them a chance," Jessie replied softly, squeezing the Doctor's hand, and her husband hit the teleport.

"Oh, excellent," Staal told them as they appeared on the ship.

"General Staal, you know what this is," the Doctor told him. "But there's one more option. You can go. Just leave. Sontaran High Command need never know what happened here."

"Your stratagem would be wise if Sontarans feared death, but we do not. At arms!"

"We'll do it, Staal," Jessie threatened. "If it saves the Earth, we'll do it."

"A warrior doesn't talk. He acts."

"And we're giving you the choice to leave."

"And miss the glory of this moment?"

"All weapons targeting Earth, sir," a Sontaran's voice announced. "Firing in twenty."

"I'm warning you," the Doctor began.

"And I salute you. Take aim!"

"You shoot us, we'll still press it," Jessie told them, wrapping one arm around the Doctor, feeling his go around her, as she placed her hand over his on the detonator. "You'll all die, Staal."

"Knowing that you die, too," Staal added.

"Firing in fifteen!"

"For the glory of Sontar! Sontar-ha! Sontar-ha!" The other Sontarans took up the chant.

Jessie shook her head. "You won't make it," she muttered, slamming the detonator and grabbing the Doctor's arm. She closed her eyes as the air exploded around them.

And they vanished in a shine of gold, and both of them slammed onto the floor of the Rattigan Academy, side by side.

Luke dropped what he'd been trying to do, and Martha ran over as Jessie's eyes fluttered, her breath coming in gasps. The Doctor rolled over, coming up on his knees to bend over her worriedly. "That's just like from Manhattan and 1913!" Martha gasped.

Jessie's head lolled. "Head," she whimpered, hearing a pounding in her head.

"Shh," the Doctor whispered, and his fingers came in contact with her temples. "Shh."

She let her body to limp as she fell asleep, the Doctor leading her through it, hopefully to recover her strength from using so much of the Vortex. She saw Martha hug the Doctor, then Donna punch him in the arm, before she let her eyes close completely.

***

"The streets are half empty," Sylvia was saying as Donna finished her mug of tea. "People still aren't driving! There's kids on bikes all over the place. It's wonderful!" She nodded to the bags of groceries she'd brought in. "Unpack that lot. I'm going to see if Suzette's all right."

Wilf winked at Donna. "I won't tell her. Best not. Just keep it as our little secret, eh?"

"Yeah," Donna agreed.

"And you go with him, that wonderful Doctor. You go and see the stars, and then bring a bit of them back for your old Gramps."

Donna kissed his cheek. "Love you."

***

"But will she be all right?" Steve insisted.

The Doctor rolled his eyes as he again checked Jessie's pulses as he laid her down on the grating close to the heart of the TARDIS. "She'll be fine, Captain," he promised. "She's home again. She'll recover easier."

"That's good," Martha said with a smile. "I'd hate for you to be a widower nearly a year after you married her."

"She dies, I die," the Doctor told her, looking up. "I die, she dies. I wouldn't even have the chance to be a widower."

Steve blinked at that when Donna came in. "How were they?" Martha asked.

"Oh, same old stuff," Donna replied. "They're fine. So, are you two going to come with us? We're not exactly short of space."

Steve looked around. "Maybe for one," he conceded. "Then it's back to SHIELD for me."

"Welcome aboard, Captain," the Doctor told him.

"I have missed all this, but, you know," Martha told them with a smile. "I'm good here, back at home. And I'm better for having been away. Besides, someone needs me. Never mind the universe. I've got a great big world of my own now!"

She headed for the TARDIS doors, but they slammed shut right in her face, sending her backwards. The Doctor blinked, and the time rotor began to go, and the resulting shaking sent them all flying. "What?" he shouted in shock. "What?!"

"Doctor, don't you dare!" Martha shouted.

"No, no, no, I didn't touch anything!" the Doctor sputtered. "We're in flight! It's not me!"

"Where are we going?" Donna asked as Steve grabbed her to stop her from flying right into the floor.

"I don't know! It's out of control!" the Doctor shouted back as he pulled Jessie closer to him as she snapped awake.

"Doctor, just listen to me! You take me home!" Martha screamed at him. "Take me home right now!"

But the TARDIS kept flying on, completely ignoring Her passengers as She went.

***

Just saying, I love UNIT's theme.

While this episode leads right into "The Doctor's Daughter," I'll still do an interlude, but this one will be from . . . the parallel world! :) I want to integrate what Skye and Saleen have been attempting to do as often as I can, so that might mean we'll get another parallel world interlude after "Midnight," and we'll definitely get one after "Turn Left," because "The Stolen Earth" picks up right after that episode.

Speaking of "The Stolen Earth" . . . anyone want to make predictions about the Metacrisis or who gets shot by the Dalek?

Also, a quick note, I think that after I post "The Doctor's Daughter," this will be on hold for a little bit. I want to finish most likely "Apocalypse Rising" before continuing so I have some distance between "Apocalypse Rising" and "Fire With Fire." The good news is that there's only five episodes left to write in "Apocalypse Rising," so this shouldn't be on hold more more than at least two weeks. Can you guys wait that long? :P

"Apocalypse Rising" should be coming your way next!