Through Thick and Thin

The Poison Sky

Thanks to Hekate1013 for favouriting this story

Gas continued to pour relentlessly out of the cars. "He's gonna choke!" Donna cried as Wilfred passed out. "Doctor!"

"It won't open!" the Doctor groaned as he tried in vain to stop the ATMOS with his sonic screwdriver.

Just then, Shareen returned with a small rock. She slammed the bonnet down and hurled the rock through the windscreen, shattering it. "Right, c'mon, Donna, let's get him outta there!" she urged and the two women had soon revived Wilfred and helped him out through the opening.

"Thanks." Wilfred wheezed as the women helped him back to the house.

"Don't mention it." Shareen replied modestly

"Nice work with that rock." Donna remarked

"Get inside the house." the Doctor warned the Humans. "Just try and close off the doors and windows."

Just then, Jenkins returned at the wheel of a black cab. " Doctor. This is all I could find that hasn't got ATMOS." he called

The Doctor ran over to the cab. "Donna, Shareen, are you two comin'?" he called

"Yeah, right with ya, Peacock." Shareen said and joined him.

Donna made to follow them but Sylvia grabbed her arm. "Donna! Don't go!" she pleaded. "Look what happens every time those two appear! Stay with us, please."

Wilfred had other ideas. "You go, my darling." he encouraged Donna

"Dad!" Sylvia hissed

"Don't listen to her." Wilfred told his granddaughter as she ran over to the taxi. "You with them. That's my girl!"

Donna climbed into the cab with the Doctor and Shareen, though she felt terribly guilty about leaving her family.

"Bye!" Wilfred waved as the cab drove off.

~8~

The cab soon arrived at the ATMOS factory and the Doctor, Shareen and Donna scrambled out. "Ross, look after yourself." the Doctor told Jenkins. "Get inside the building."

"Will do." Jenkins acknowledged. "Greyhound Forty to Trap One. I have just returned the Doctor to base safe and sound." he reported into his radio, then he drove into the factory while the trio proceeded on foot.

"The air is disgusting!" Donna coughed

"It's not so bad for me." the Doctor remarked. His respiratory bypass system was protecting him from the worst of the gas.

"Huh, you're not Human!" Shareen grunted. "Gah, it's like that motorway on New Earth out here!"

"Go on, get inside the TARDIS." the Doctor advised both women. "Oh, never given you a key, Donna!" He pulled out a key and gave it to Donna. "Keep that. Go on, that's yours. Quite a big moment really." he commented

"Yeah, maybe we can get sentimental after the world's finished chokin' to death!" Donna retorted, pocketing her new key.

"Good idea." the Doctor conceded. "See ya both in a bit."

"Why? Where're you goin'?" Shareen asked him

"To stop a war." the Doctor replied and hurried off towards the lorry while Donna and Shareen headed off towards the TARDIS.

Donna unlocked the door with her new key then the two women stepped inside the box and took deep lungfulls of the cleaner air. "Better." Donna wheezed

"You can say that again." Shareen agreed. "Whoo! I am not going out there again!"

~8~

Meanwhile, the Doctor rushed into the lorry office. "Right then, here I am, good." he said. "Whatever ya 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?" Mace asked him

"I've got the TARDIS, I'm gonna get on board their ship." the Doctor replied. In the corner of his eye, he saw Martha press a button on her phone as soon as he'd said that. He could immediately sense that this was not Martha Jones. She seemed off and he suspected that she had been replaced by a Sontaran clone. "Come on!" he called to her, deciding it was best to keep her where he could see her.

~8~

Donna and Shareen were waiting in the TARDIS when the box suddenly rocked. "What's happening?" Donna gasped

"Search me." Shareen replied, grabbing hold of a Y-beam to stop herself from falling over. The TARDIS then settled. "Hang on, I'll take a butcher's outside." Shareen said and moved to the door. She opened it to see that the TARDIS was no longer on Earth and was instead on the Sontaran ship. Fortunately, the Sontarans were all too busy to notice her.

Shareen immediately recognised General Stall. "None of the humans can guess our true purpose." he said arrogantly to Commander Skorr.

Shareen immediately shut the door as quietly as she should and locked it. "What is it?" Donna asked her, noticing the look of worry on the young woman's face.

"Donna..." Shareen began, "I don't wanna worry ya, but we're on the Sontaran's spaceship."

"What?!" Donna gasped in horror. "You are kiddin' me!"

"I wish I was." Shareen said numbly. "I've just looked and there's thousands of 'em out here. They must've teleported us up or something."

"So what're we gonna do?" Donna asked frantically.

"Have a sit down?" Shareen muttered, slumping down against the door. "Cosmic." she muttered. "Cos-bloody-mic!"

~8~

Meanwhile, the Doctor and the Martha clone were at the empty spot where the TARDIS had been taken from. "But... Where's the TARDIS?" the Martha clone asked

"Taste that, in the air." the Doctor commented. "Yech! That sorta 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? Sorry, no offense, but come on!" He watched the Martha clone closely for her reaction. He knew that the real Martha Jones would retort to his comment, but this clone didn't seen fazed at all.

"So, what do we do? she asked in a monotone voice

"Well... it's shielded, they could never detected it." the Doctor said, and looked at the clone again to see if she'd ask him why he'd just called the TARDIS 'it' instead of 'her', but again she seemed unfazed

"What?" she asked

"I'm just wanderin', have ya phoned ya family an' Tom?" the Doctor asked, testing her again.

"No, what for?"

"The gas, to tell 'em to stay inside."

"Course I will, yeah." 'Martha' said hastily. "But what about Shareen and Donna, I mean, where are they?"

"Oh, she's gone home an' Shareen went to find her family." the Doctor lied, testing the clone again. "They're not like you. They're not soldiers. Right, so, avanti!" And he led the way back to the lorry, now 100% positive that 'Martha' was a Sontaran clone. If she were the real Martha, she'd have taken offence to being called a soldier, she wouldn't have swallowed his lies about Shareen and Donna, and she would've questioned his use of a different expression. They were soon back at the lorry. "Change of plan." he said to Mace

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

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

"We're working on it." Zara replied from where she was working at a computer.

"It's harmful, but not lethal until it reaches 80% density." a blonde woman in an officer's uniform reported, standing up. "We're having the first reports of deaths from the centre of Tokyo city."

"And who are you?" the Doctor asked her

"Captain Marion Price, sir." she saluted

"Oh, put ya hand down, don't salute." the Doctor rolled his eyes. He could never stand the military formality that predominated U.N.I.T

"Jodrell Bank's traced a signal, Doctor," Mace announced, "coming from 5,000 miles above the Earth. We're guessing that's what triggered the cars." he gestured to the screen, which was displaying a red blip

"The Sontaran ship." the Doctor realised

"NATO has gone to Defcon One." Mace said. "We're preparing a strike."

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

"You're not authorised to speak on behalf of the Earth." Mace said pompously

"I've got that authority, I earned that a long time ago." the Doctor retorted, and flashed his sonic screwdriver on the com system. "Calling the Sontaran command ship under Jurisdiction Two of the Intergalactic Rules of Engagement. This is the Doctor."

~8~

The Doctor's transmission was picked up by the TARDIS. As the monitor sprang to life, Shareen swore that she could see the face of Rose Tyler for a split second before it changed to a shot of the Doctor and the colonel. "Doctor, we're here!" Donna said. "Can you hear us?"

"No, I don't think he can." Shareen realised. "He must be callin' the spudheads and we're just picking up the transmission."

Donna gave her a somewhat bewildered look.

"What? Travellin' with Peacock, ya pick up a few things." Shareen shrugged.

General Staal then appeared on screen. "Ah, Doctor. Breathing your last?" he taunted

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

"Yeah, loving the diplomacy, thanks." the Doctor rolled his eyes then turned back to the screen. "So, tell me, General Staal, since when did you lot become cowards?"

"How dare you!" Staal said, outraged.

"Oh, THAT'S diplomacy?" Mace questioned the Doctor, who just slouched down in a chair with his feet on the desk.

"Doctor, you impugn my honour!" Staal fumed

"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 yet you're sitting up above watching it die."

"Which brings us to our TV Burp poetry corner." Shareen joked, making Donna chuckle

"Where's the fight in that?" the Doctor continued. "Where's the honour? Or are you lot plannin' something else? Because this isn't normal Sontaran warfare. What're you lot up to?"

"A general would be unwise to reveal his strategy to the opposing forces." Staal replied stiffly

"Ah, the war's not going so well, then. Losing, are we?" the Doctor taunted

"Such a suggestion is improbable." Staal blustered

"What war?" Mace asked

"The war between the Sontarans and the Rutans. It's been raging, far out in the stars, for fifty thousand years." the Doctor told him, then turned back to the screen. "50,000 years of bloodshed, an' for what?"

"For victory." Staal answered. "Sontar-ha!" he began to chant and other Sontarans joined in

~8~

The Doctor rolled his eyes at the Sontarans' chanting. "Gimme a break." he muttered and soniced the screen, changing it to a kid's TV show.

Mace wasn't amused by the Doctor's antics. "Doctor, I would seriously recommend that this dialogue is handled by offical Earth representation." he grumbled

The Doctor just waved him off and soniced the screen again, changing it back to the Sontaran transmission. "Finished?" he asked Staal dryly

"You will not be so quick to ridicule when you see our prize. Behold!" Staal retorted, moving aside to reveal the TARDIS behind him. "We are the first Sontarans in history to capture a TARDIS."

"As prizes go, that's... Noble." the Doctor said. "As they say in Latin, Donna nobis pacem et Shareen."

~8~

"That's us! We're here!" Donna said, realising that the Doctor was talking to her and Shareen.

"Did you never wonder about its design?" the Doctor said to Staal. "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." And he made a phone gesture with his hand, subtly signalling to his companions.

Shareen got the message and took her phone out in readiness. "But who do we phone?" Donna pointed out.

"All you have communicated is your distress, Doctor." Staal said, oblivious to the subtle messaging.

"Big mistake, though, showin' it to me." the Doctor continued. "Cos' I've got a remote control." And he waggled his sonic screwdriver between his fingers.

"Cease transmission!" Staal ordered, and the transmission ended.

"He wants us to phone him, but what's his number?" Donna asked Shareen.

"He hasn't got a phone." Shareen replied. "I think we'll have to wait for him to phone us. Just hope he doesn't take too long. We can't hide in here forever." The TARDIS suddenly shook again. "Oh, now what?" Shareen grumbled.

"I think the Sontorans are movin' us." Donna realised.

~8~

"Oh, well." the Doctor shrugged as he got up

"That achieved nothing." Mace grumbled

"Oh, you'd be surprised." the Doctor shrugged nonchalantly.

~8~

While they waited for the Doctor to get in touch with them, Donna and Shareen decided to contact their families, with Shareen calling her grandparents in Tenerife while Donna called her home. "Mum, are you alright?" she asked

"Donna!" Sylvia gasped over the other end. "Where are you, sweetheart?"

"Is that her?" Wilfred's voice called out from nearby

"Oh, just finish the job." Sylvia told him, then turned back to the phone. "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 workin' on it, mum." Donna reassured her. "They're gonna fix it, I promise."

"Oh, like YOU'D know, you're so clever!" Sylvia scoffed

"Oh, don't start." Donna huffed. "Don't please."

"I'm sorry. I wish you were HERE."

"Now, come on Sylvia, look. That DOESN'T help." Donna heard Wilfred say before taking the phone himself. "Donna? Where are you?" he asked

"Sorta hard to say." Donna replied, glancing around the console room. "You alright?"

"Yeah, fighting fit, yeah. Are they with you, the Doctor and Shareen?"

"Shareen is, but the Doctor isn't." Donna replied

"Look, you promised he was going to look after you." Wilfred reminded

"He will, Gramps." Donna reassured him. "There's... something he needs us 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 one man stop all that?"

"Trust me. He can do it." Donna said bravely

"Yeah, well, if he doesn't, you tell him he'll have to answer to ME."

"I will." Donna smiled. "Just as soon as I see him, I'll tell him." She ended the call and turned to Shareen, who was on her phone talking to her grandparents.

"Yeah, love you too, Gramps." Shareen said into her phone. "Talk to ya later, I hope. Bye!" And she ended the call.

"How are they?" Donna asked her

"They're alright." Shareen replied. "Their house has air-con so they've holed up inside. The smog outside's bad, though. What about your family? Are they alright?"

"They're battening down the hatches." Donna replied. "I just wish there was something we could do. I feel so helpless just stuck here."

"Me too." Shareen sighed. "I'm gonna get my pen. Ya never know, Peacock might want us to sonic something." And she hurried off to her bedroom to retrieve her sonic pen.

~8~

In the lorry, the Doctor strode over to join Zara, who was reading a clipboard with the gas analysis. "Well?" he asked her

"There's carbon monoxide, hydrocarbons, nitrogen oxides but 10% unidentified." Zara reported. "Some artificial heavy element we can't identify. You ever seen anything like it?"

The Doctor shook his head. "Must be something the Sontarans invented. This isn't just poison. They need this gas for something else. What could that be?" he wandered

"Launch grid active." Captain Price announced, pulling the Doctor from his thoughts.

"Positions, ladies and gentlemen." Mace ordered. "Defcon one initiatives in progress."

"What?!" the Doctor glared, realising the Humans were preparing a nuclear strike. "I told you not to launch!" he stormed up to Mace

"The gas is at 60% density. 80% and people start dying, Doctor. We've got no choice." Mace defended.

The countdown to launch commenced. The Doctor ran a hand through his hair in exasperation. When U.N.I.T changed it's name from United Nations Intelligence Taskforce, they should've changed it to Unified Idiot Taskforce, since it seemed there wasn't any intelligence anymore. "You're making a mistake, colonel." he said as the countdown ticked down. "For once, I hope the Sontarans are ahead of you."

"Huh, I don't see you coming up with any better ideas." Zara snarked at him.

"All systems locked and co-ordinated." Price announced. "Launching in 10, 9, 8, 7, 6..."

"God save us all." Mace muttered

As Price continued to count down, nobody noticed the Martha clone pressing a button on her phone. As Price reached zero, the screens suddenly went black. "What is it?" Mace asked urgently. "Did we launch? Well, did we?"

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

"Can we override it?"

"Trying, sir."

"Missiles wouldn't even dent that ship, so why are the Sontarans so keen to stop them?" the Doctor muttered, then turned to the Martha clone. "Any ideas?"

"How would I know?" she answered hastily, earning a raised brow from the Doctor. This clone was doing a pretty shoddy job of acting like Martha.

Suddenly, Jenkins' voice came over the radio, "Enemy within! At arms! Greyhound 40 declaring absolute emergency. Sontarans within factory grounds, east corridor six."

Mace answered the radio. "Absolute emergency. Declaring code red. All troops, code red."

"Get them outta there!" the Doctor urged, knowing those men didn't stand a chance against Sontarans, but Mace didn't listen.

"All troops, open fire." he ordered

Moments later, Jenkins came back over the radio, "The guns aren't working. Inform all troops, standard weapons do not work." Then came the sound of laser weapons fired, followed by men's screams. "Tell the Doctor it's that cordolaine signal." Jenkins said urgently. "He's the only one who can stop them." There was another burst of laser fire and the line went dead.

"Greyhound 40, report. Over." Mace said, not realising that all that section were dead due to his refusal to listen to the Doctor. "Greyhound 40, report. Greyhound 40, report!"

"He wasn't Greyhound 40, his name was Ross." the Doctor glared, angry at this military moron who had just let good men get slaughtered. "Now listen to me, and GET THEM OUT OF THERE!" he bellowed

Mace finally saw sense. "Trap 1 to all stations, retreat." he ordered. "Order imperative, immediate retreat."

~8~

U.N.I.T troops fled from the factory. Some made it, but others were not so lucky. The Sontarans indiscriminately gunned down any Human they came across. Commander Skorr led the massacre, relishing in the bloodshed. "This is too easy. They're running like slimebait from a speelfox. This isn't war, this is sport!" he gloated.

~8~

"They've taken the factory." Mace realised

"Why? They don't need it. Why attack now? What're they up to?" the Doctor wandered. "Times like this, I could do with the Brigadier." He looked to Mace. "No offence."

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

"Launch grid back online." Price announced and everyone turned back to the screens, which were online again. In the corner of his eye, the Doctor saw the Martha clone press a button on her phone again and the screens promptly died again.

"Oh, for God's sake!" Zara grumbled. "What keeps doing that?!"

"They're inside the system, sir." Price told Mace. "It's coming from U.N.I.T itself."

"Trace it." Mace ordered. "Find out where it's coming from, and quickly. Gas levels?"

"66% in major population areas and rising." Price replied

Zara, Mace and the Doctor went into the lorry's private office area to discuss the situation. "Why are they defending the factory only after we were inside?" Mace wandered

"Because they wanted U.N.I.T here." the Doctor pondered, working it out. "You gave them something they needed. Something now hidden inside the factory. Something precious."

"Any ideas what is it?" Zara asked him rhetorically

"We've got to recover it." Mace determined "This cordoline signal thing, how does it work?"

"The bullets. It causes expansion of the copper shell." the Doctor replied

"Excellent. I'm on it." Mace said and left the room

"For the billionth time, you can't fight Sontarans!" the Doctor called after him.

"Just watch us." Zara told him

The Doctor turned to her. "Phone. Have ya got a phone?" he asked quietly so that the Martha clone couldn't overhear."

"Why?" Zara asked suspiciously

"Donna an' Shareen are trapped on the Sontaran ship an' I need to give 'em instructions to help me out." the Doctor replied

"Huh, what's Shareen gonna do? Sing 'em to death?" Zara snarked.

"Just... gimme ya phone." the Doctor rolled his eyes.

"Alright, but don't use up all my credit." Zara huffed and begrudgingly handed over her mobile.

~8~

In the TARDIS, Shareen's mobile rang and she answered. "Hello?"

"Shareen? Are ya there?" the Doctor asked

"Peacock! About bloody time!" Shareen exclaimed, putting the phone on loudspeaker so that Donna could hear. "Where are ya?"

"Still at the factory." the Doctor replied. "But don't worry, I've got my secret weapons."

"What're they?" Donna asked

"You two." the Doctor replied

"Somehow I don't find that particularly reassuring." Shareen muttered

"Can't you just zap us down to Earth with that remote thing?" Donna asked the Doctor

"Yeah, I haven't got a remote, though I really should." the Doctor replied. "But I need ya both on that ship, that's why I made 'em move the TARDIS. I'm sorry, but you've both gotta go outside."

"You're kidding." Shareen stared.

"But there's Sonteruns out there." Donna protested

"Sontarans." the Doctor corrected. "But they'll all be on battle stations right now. They don't walk around havin' coffee. I can talk ya both through it."

"And what do we do if those spudheads find us?" Shareen pointed out

Zara then said something which neither Shareen or Donna heard but it didn't sound particularly reassuring.

"Alright. Zara, I'm handlin' this." the Doctor told Zara then turned back to the phone. "I know, and I wouldn't ask, but there's nothing else I can do. The whole planet is choking."

"What d'ya need us to do?" Donna asked, apprehensively walking towards the TARDIS doors.

"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." the Doctor replied

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

"And I don't know jack sh*t about spudhead technology." Shareen added

Zara made another snide remark at this. "Enough!" the Doctor chided her then spoke to his companions. "Ladies! Stop talking about yourselves like that. You can both do this, I promise." he reassured them.

Donna went to the doors to see if the coast was clear. She saw two Sontarans standing on guard outside the TARDIS "There's a couple of Sonterans... Sonatans." she hastily corrected

"Did they see you?" Shareen asked

"No, they've got their backs to us."

"Good, that means we can surprise 'em." Shareen said and spoke into her phone. "Doctor, when we were at the school, you said the spudheads had a weakness on the back of the neck, didn't ya?"

"Yes, it's the probic vent." the Doctor replied. "It's the thing that looks like a plug. One blow to the vent knocks 'em out."

"But they're gonna kill us." Donna protested

"Well, they're not gonna get me without a fight." Shareen said determinedly, walking over to the console and grabbing the Doctor's mallet and hammer. "C'mon, let's play whack-a-spud." And she handed the mallet to Donna.

The two women cautiously crept out of the TARDIS, glad they were both wearing trainers. They snuck up behind the two Sontarans and walloped their probic vents with their melee weapons, sending the two Sontarans crashing to the floor unconscious. "Back of the neck!" Donna grinned. "What now?"

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

"What does it look like?"

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

"Can't see it, but I've found a door." Shareen said

"Should be a switch by the side." the Doctor told her

"Yeah there is. But it's Sontaran shaped, you need three fingers." Donna pointed out

"Good thing I've got this then." Shareen said, taking out her sonic pen. She aimed it at the door, pressed the button and the door slid open.

"We're through." Donna reported to the Doctor.

"Oh, you're both brilliant, you are!" the Doctor said

"Too right we are!" Shareen smirked. "Right, we're looking for that feed thing now."

~8~

At that moment, the Doctor saw Mace re-enter the lorry. "Gotta go. Keep the line. Good luck." he said, slipping Zara's phone into his pocket and went over to the colonel.

"Counter attack." Mace announced to everyone

"I said you don't stand a chance!" the Doctor told him

"Positions. That means everyone." Mace said, tossing a gas mask to the Doctor

"You're not going without me." the Martha clone said to the Doctor

"Wouldn't dream of it." the Time Lord replied, grabbing his coat.

"And you've got my phone so I'm not letting you out of my sight." Zara said.

~8~

Donna and Shareen snuck through the corridors of the Sontaran ship. Suddenly, they heard stomping footsteps, so they both hid behind wall pillars as a platoon of Sontarans marched past. Once the coast was clear, the women resumed their search, Shareen using her sonic pen to bypass any locked doors they came across.

~8~

At the factory, everyone was gathered outside for a briefing. All were wearing gas masks including the Doctor, though he didn't need it, thanks to his respiratory bypass system, but there was a joke he was dying to make. Mace was showing him a rifle. "Latest firing stock." he explained. "What do you think, Doctor?"

"Are you my mummy?" the Doctor joked

Mace was not amused. "If you could concentrate." he grumbled, then got to business. "Bullets with a rad-steel coating, no copper surface. Should overcome the cordoline signal."

"But the Sontarans have lasers." the Doctor reminded. "Ya can't even see in this fog, the night vision doesn't work."

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

"No change there, then." the Doctor retorted

Zara said something, though thanks to her gas mask, it came out as a muffled noise.

Mace ignored the Doctor and took off his gas mask to address his troops. "Attention, all troops. 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 grabbed a radio. "Trap 1 to Hawk Major, go, go!"

A loud noise came from the sky, and everyone looked up to see a large shape begin to appear through the smog.

"It's working." Mace said into his radio. "Engines to maximum."

The smog began to clear, and the Doctor could now recognise what the shape was "It's the Valiant!" he realised

"U.N.I.T ship Valiant reporting for duty, Doctor." Mace said proudly. "With engines strong enough to clear away the fog."

Sure enough, the Valiant's engines completely dispersed the gas around the area, allowing everyone to take their gas masks off. "Woah, that is brilliant!" the Doctor praised. He had to admit, that was good thinking by Mace. Perhaps U.N.I.T still had some intelligence after all.

"Still think we can't fight those potatoheads?" Zara asked smugly. "Watch and learn, Doctor."

"Valiant, fire at will." Mace ordered into his radio, and the ship fired a massive energy weapon at the factory, destroying a good part of it and taking a fair few Sontarans with it. The ground troops then started their attack too. They stormed the factory, and with their steel-lined bullets, they were able to give the spuds a taste of their own medicine. Mace and the Doctor followed them in "North and east secure." Mace observed. "Doctor?" And he and his troops rushed off in one direction.

"Shareen, Donna, hold on, I'm coming." the Doctor said into the phone. He started to go in another direction when the Martha clone appeared

"Shouldn't we follow the colonel?" she asked

"Nah, you and me, Martha Jones. Just like old times." he tested.

Once again, the clone failed the test as she failed to point out that Shareen had always been there when Martha was travelling with the Doctor.

The Doctor pulled out his sonic screwdriver and scanned for alien technology, getting a positive result. "Alien technology, this a-way!" he said and rushed off following the signal, the clone following him.

"Oi! Wait for me!" Zara grumbled as she brought up the rear, her pencil skirt and heels making it hard for her to keep up.

The signal led them to the factory cellar. "No Sontarans down here." the Doctor observed. "They can't resist a battle. Here we go." They entered the clone lab where the real Martha Jones was in an hypnotic sleep.

"What the hell?!" Zara stared

The Doctor rushed over to the real Martha. "Ooh, Martha, I'm so sorry." he sighed and checker her pulse. "Still alive." he said in relief, then heard the sound of a gun clicking behind him, and in the corner of his eye, he could see the clone aiming a pistol at him. "Am I supposed to be impressed?" he said dryly

"Wish you carried a gun now?" the clone spat

"You!" Zara spat, and made to rush the clone but the clone aimed her pistol at her instead.

"No false moves!" the clone threatened, then shifted her aim back to the Doctor. "I've been stopping the nuclear launch all this time." she said, telling the Doctor what he already knew.

"Doing exactly what I wanted." he said. "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."

"How did you know she's a clone?" Zara asked

"Oh, right from the start." the Doctor replied. "You cared nothing for ya family, you accepted my lie about Shareen not being with me, and frankly, you smell." he told the clone. "You might as well wear a t-shirt sayin' 'Clone'. Though not in front of Captain Jack. You remember him, don't ya? Cos' you've got all her memories. That's why the Sontarans had to protect her, to keep you inside U.N.I.T. Martha Jones is keepin' you alive." And with that, he yanked a device off the real Martha's head, causing her to wake up and the clone to drop to the floor in agony. Zara quickly took over the gun while the Doctor put a comforting arm around Martha. "It's alright, it's alright." he soothed. "I'm here, I'm here. I've got you, I've got you."

"There was this thing, Doctor." Martha panted. "This alien, with this head..." Then she saw her clone, who was on the floor, dying. "Oh, my God. That's me!" she exclaimed

Just then, the mobile rang again. "Oh, blimey, I'm busy." the Doctor said, and answered the phone. "Have ya found it yet?"

~8~

"Yes!" Shareen answered, she and Donna standing next to the Sontaran teleport feed. "Now what do we do now?"

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

"Huh, is that it?" Shareen shrugged, taking out her sonic pen and using it to remove the seals on the cover.

~8~

Commander Skorr walked through a corridor in the factory when Colonel Mace came up behind him. "You will face me, sir!" Mace demanded

Skorr turned to face him, pleased for the fight and Mace promptly unloaded his pistol into the Sontaran, avenging the deaths of Jenkins and the other U.N.I.T troops the Sontarans had slaughtered in cold blood.

Skorr crashed to the floor, mortally wounded. "Wonderful." he said with his last breath before he died.

~8~

The clone lab had a teleport pod and the Doctor and Zara were busy tinkering with it. While they worked, Martha approached her clone. "Don't touch me!" the clone spat

"It's not my fault." Martha told her. "The Sontarans created you. But.. you had all my memories."

"You've got a brother, sister, mother and father." the clone noted, getting weaker and weaker.

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

"You love them." the clone noted

"Yes." Martha nodded. "Remember that?"

"The gas!" the Doctor shouted over from where he and Zara were working. "Tell us about the gas."

"He's the enemy!" the clone snarled

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

"Caesofine concentrate. It's one part of bosteen, two parts probic 5."

"Clonefeed!" the Doctor realised. "It's clonefeed!"

"What's clonefeed?" Martha asked him

"Like amniotic fluid for Sontarans. That's why they're not invadin'. They're convertin' the atmosphere. Changin' the planet into a clone world, Earth becomes a great big hatchery. Cos' the Sontarans're clones, that's how they reproduce. Give 'em a planet this big, they'll create billions of new soldiers. This gas isn't poison, it's food!"

"But why here?" Zara wandered. "If they want a planet to make clones, why can't they pick on Saturn or something?"

"My heart..." the clone panted. "It's getting slower

"There's nothing I can do." Martha sighed

"In your mind, you've got so many plans." the clone croaked. "There's so much you wanna do."

"And I will." Martha said. "Never do tomorrow what you can do today. that's what mum says, cos'..."

"Cos' you never know how long you've got." the clone finished. "Martha Jones. All that life..." she drew her last breath and died. The real Martha looked at her sadly, before retrieving her engagement ring.

~8~

Donna and Shareen finished up their work on the blue switches. "Blue switches done." Donna said into the phone. "What now?"

"Nearly done down here." the Doctor answered. "Give us two ticks."

Just then, a door slid open and a platoon of Sontarans marched in. "Sh*t! Peacock, they've found us!" Shareen hollered. "Bloody hurry up down there!"

~8~

The Doctor soniced the clone lab's teleport pod and Donna and Shareen appeared within it. "That was too close!" Shareen panted in relief at the close shave.

"Have I ever told you how much I hate you?" Donna said to the Doctor.

"Hold on, hold on. Got to bring the Tardis down." the Doctor said, sonicing the pod again, this time to bring the TARDIS back to her original position in the alley. "Right, now, Martha, you coming?" he asked as he joined Donna and Shareen in the pod.

"What about this nuclear launch thing?" Martha asked him, holding up the phone her clone had been using

"Just keep pressin' N." the Doctor replied. "Keep those missiles on the ground."

Just then, Donna and Shareen caught side of the dead clone. "Why're there two Marthas?" Shareen asked

"Yeah, long story." the Doctor waved her off

"Shareen, it's alright, it's me. The real me." Martha reassured her friend as she joined them in the pod.

"Here we go. The old team, back together. Well, the new team." the Doctor said

"We are not goin' back on that ship!" Donna demanded

"No, no, no," the Doctor reassured her, "I needed to get the teleport working so we could get to..." He operated the controls and they teleported away.

Zara was left behind. "Oh, go off without me why don't ya?" she grumbled and went off to see what the rest of U.N.I.T were doing.

~8~

The Doctor, Martha, Donna and Shareen appeared in the teleport pod in the Rattigan Academy. "...here." the Doctor finished. "The Rattigan Academy, owned by..."

They all looked round to see Luke pointing a pistol at them. "Don't tell anyone what I did!" he blustered. "It wasn't my fault! The Sontarans, they lied to me!"

Shareen grabbed the gun from him. "I'll have that if ya don't mind, eh?" she said smoothly and tossed the gun away.

"Ya know, that coat sorta works." Donna remarked to Martha, who was wearing the Doctor's coat over the medical the Sontarans had forced her in

"Feel like a kid in my dad's clothes." Martha replied.

"Oh, well, if ya callin' Peacock 'dad' then you're definitely over him." Shareen remarked, and all three women shared a laugh.

~8~

Meanwhile, the gas smog was getting unbearable. In the Noble house, Wilfred put a towel by the living room door to block out the worst of it, then went to comfort his scared daughter. "Oh, my little girl. Come on, we'll be alright." he soothed. "We'll be alright. Donna said so. She promised. Come on, darling. It's alright."

~8~

At the Rattigan Academy, the Doctor was now busy assembling a device out of the equipment in the lab. "That's why the Sontarans had to stop the missiles." he explained to the Humans. "They were holding back. Cos' caesofine gas is volatile, that's why they had to use you to stop the nuclear attack." he told Martha. "Ground-to-air engagement could've sparked off the whole thing."

"What, like set fire to the atmosphere?" Martha questioned

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

"They promised me a new world." Luke said bitterly

"You were building equipment, ready to terraform El Mondo Luko so that humans could live there and breathe the air with this." the Doctor said, gesturing to the device he'd built. "An atmospheric converter." He grabbed the converter and they all went outside to see the London skyline practically invisible from the thick smog

"That's London." Donna stared in horror. "You can't even see it. My family's there."

"Can that thing get rid of all this gas, Peacock?" Shareen asked the Doctor

"Yes, if I can get this on the right setting." the Doctor replied, pressing a few buttons on the converter.

"Doctor, hold on. You said the atmosphere would ignite." Martha reminded him

"Yeah, I did, didn't I?" the Doctor grinned and pressed a button on the control pad. An energy pulse zoomed up into the gas-covered sky and ignited. The Doctor crossed his fingers as a fireball spread across the sky. "Please, please, please, please, please, please, please." he muttered under his breath.

~8~

Wilfred and Sylvia looked out of their front window to see the sky on fire.

~8~

Zara joined Mace and Price at the factory to watch the burning sky. "What the hell?!" she stared

~8~

The fire spread across Earth's upper atmosphere then cleared, revealing clear blue skies without a trace of gas left. Wilfred and Sylvia cautiously stepped outside their house to find fresh air awaiting them. They both cheered and celebrated.

~8~

At the factory, U.N.I.T celebrated too. "Yes!" Zara cheered, pumping her fist in the air while Mace and Price kissed each other before quickly pulling away in embarrassment.

~8~

"He's a genius!" Luke breathed in amazement

"Just brilliant!" Martha agreed

"Peacock, I could bloody kiss you!" Shareen laughed. "Except I won't, cos', ya know, ew!"

"Now we're in trouble!" the Doctor said, grabbing the converter and running back into the building.

"What d'ya mean?" Donna asked as she and the others followed him.

"Right. So... Donna, Shareen, thank you for everything." the Doctor said, stepping inside the teleport pod. "Martha, you too. Oh, so many times. Luke, do something clever with ya life."

"You're saying goodbye." Donna realised

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

"You're going to ignite them." Martha realised

"You'll kill yourself!" Donna breathed in horror

"Are you insane, Peacock?!" Shareen burst out

"Just send that thing up on it's own." Martha protested. "I don't know, put it on a delay."

"Or just get U.N.I.T to nuke 'em or something." Shareen added

"I can't." the Doctor told them

"Why not?" Donna challenged

"I've got to give them a choice." the Doctor said gravely.

"Oh, for God's sake, Peacock, they're clones!" Shareen pointed out. "You said yourself they're grown in batches of millions. They're not gonna care if they get blown up; they'll just clone a million more to replace 'em, but there's only one of you!"

"I know, but I've got to try." the Doctor sighed and activated the teleport.

~8~

The Doctor appeared on the Sontaran ship. "Oh, excellent!" Staal crowed

"General Staal, you know what this is." the Doctor said, putting the converter down. "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." Staal retorted. "At arms!"

"I'll do it, Staal. If it saves the Earth, I'll do it." the Doctor challenged

" A warrior doesn't talk, he acts." Staal goaded

"I am giving you the chance to leave." the Doctor persisted

"And miss the glory of this moment?" Staal retorted

"All weapons targeting Earth, sir." a Sontaran reported over the com. "Firing in 20."

"I'm warning you." the Doctor said

"And I salute you." Staal answered. "Take aim!" and his troops aimed their weapons at the Time Lord

"Shoot me, I'm still going to press this. You'll die, Staal." the Doctor threatened

"Firing in 15." the Sontaran over the com announced

"For the glory of Sontar!" Staal crowed and began to chant. "Sontar-ha! Sontar-ha! Sontar-ha!"

The other Sontarans joined in. "Sontar-ha! Sontar-ha! Sontar-ha! Sontar-ha! Sontar-ha! Sontar-ha! Sontar-ha!"

"I'll do it!" the Doctor threatened

"Then do it!" Staal goaded, knowing that the Doctor didn't have the balls to carry out his threat.

~8~

Back on Earth, Luke was fiddling with the teleport. "What're you doing?" Martha asked him

"Something clever." Luke replied and activated the teleport, switching places with the Doctor. The Sontarans promptly stopped chanting at the sight of Luke. "Sontar-ha!" he spat and slammed his hand down on the ignition button.

The Sontaran ship exploded in a huge ball of fire, taking Luke and the Sontarans with it.

~8~

The Doctor appeared in the teleport pod at the Rattigan Academy. When he saw that Luke was missing, realisation dawned on him and he sat down at the edge of the pod, overcome with guilt at the death of the young man thanks to his stupid idea. Martha sat down beside him and squeezed his arm in comfort. Donna walked over to them and gave the Doctor a whack for his stupidity then sat down too. Shareen meanwhile turned and left without a word.

~8~

Next day, Shareen walked through the ATMOS factory complex to find U.N.I.T busy cleaning up the mess and taking away the bodies of the dead personnel and Sontarans. She found Zara busy trying to remove the ATMOS fittings from a jeep. "Zara?" she called

Zara looked round. "Oh, it's you. What d'ya want?" she asked coldly

"Just dropped by to see how ya doin'." Shareen replied

"I'm busy. That's how I'm doing." Zara retorted. "So off ya go. Run off again, that's a good girl."

Shareen rolled her eyes at her sister's attitude. "Zara, I know ya jealous of me, but..."

"Oh, don't flatter yourself." Zara scoffed. "I might be stuck here cleaning up but I'm still better than you! You can travel with the Doctor all ya like but you're still a loser. You were born a loser you are a loser an' you'll always be a loser."

"And you're a b*tch." Shareen retorted. "Have fun cleaning up all those dead spudheads." And she headed off back to the TARDIS.

~8~

Meanwhile, Donna was at home telling her granddad what had happened. Sylvia entered, having gone down to the shop. She'd gone on foot as everyone was giving their cars a wide berth in the wake of yesterday's events. "The streets are half-empty. People still aren't driving." she told her family. "There's kids on bikes all over the place. It's wonderful. Unpack that lot, I'm going to see if Suzette's all right." And she went off into the living room.

"I won't tell her." Wilfred said to Donna. "Best not. Just keep it as our little secret, eh?"

"Yeah." Donna nodded

"And you go with them, that wonderful Doctor and that Shareen girl." Wilfred encouraged. "You go and see the stars, and then bring a bit of 'em back for your old Gramps."

Donna nodded, stood up to hug him and kissed his head. "Love you." she said and left the house, fighting back tears.

~8~

Shareen and Martha were chatting to each other in the TARDIS when Donna arrived. "How were they?" Martha asked

"Oh, same old." Donna replied, wiping away a tear and trying to sound casual. "They're fine. So, you going to come with us? We're not exactly short of space"

"Yeah, and with all three of us here, Peacock'll think twice before being an arsehole again." Shareen added

"Oi!" the Doctor grumbled from where he was idling by the console.

"Oh, I have missed all this," Martha said to Donna and Shareen, "but, you know. I'm good here, back at home. And I'm better for having been away. Besides," she held up her hand with 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 door, only for it to slam shut in front of her. Then the TARDIS took off on her own account, sending everyone scrambling to find something to hold on to. "What? What?!" the Doctor spluttered in surprise.

"What the hell did ya do, Peacock?!" Shareen glared

"Doctor, don't you dare!" Martha glowered

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

"Where're we goin'?" Donna called

"Dunno, she's out of control." the Doctor replied, wrestling with the controls.

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

But the TARDIS had other ideas and continued to fly on through time and space on her own accord, taking the quartet into the unknown.

Author's notes: And that's The Poison Sky in the bag. As promised, we get to see more of Zara in this chapter. She's not the most pleasant person to be around, though she did make a couple of valid points about the Doctor. He wasn't exactly at his best in this two-parter so having someone call him out on it was justified. Note that just as with Gazelle and Iris, Shareen ended up on the Sontaran ship with Donna. The reason why I do this is because I feel that having the OC end up with Donna is better than having them on Earth with the Doctor, who spends most of the episode hanging around in the lorry being an arsehole to Colonel Mace, whereas if they're with Donna, they get to do something practical. Plus it means Shareen doesn't have to put up with Zara! So, hope you like this chapter and hope to see ya next time.