Chapter 4: Carmageddon:

Ross hammered hard on the windows. But they were designed to be shockproof, and would take a lot more force to shatter. He didn't dare try and shoot them with the car bouncing around the way it was, as it sped across the waste ground towards the river.

The Doctor leaned into the satnav box. "You're programed to disobey my instructions, right? Everything I say, you'll do the opposite?"

"Confirm." Said Lucy.

"Then drive us into the river! Go on! I order you to drive us into the river!"

The box whirred for a few seconds, as the river came ever closer. "Confirm." It said and the brakes came on, bringing the jeep to a halt right on the riverbank.

Finding the doors unlocked, the Doctor and Ross wasted no time in bailing out and running for cover. Not least because Lucy was confused by these new set of orders, flashing up error messages and running the cooling fans at maximum.

"Turn left. Right. Turn left right leftrightleftright…" Finally, the box overheated, going up in a tiny plume of smoke and a couple of sparks.

"Is that it?" Said the Doctor, disappointed.

The malfunctioning satnav had caused the dot on the Sontarans' screen to appear in the middle of the river. They watched as it winked out.

"Mission accomplished sir. The Doctor is dead."

"Excellent. Then we shall proceed." Said Staal. He hit a button on his intercom. "Is the operative in place?"

Martha's clone had pulled on her human self's uniform and engagement ring, as well as rinsing the embiotic fluid off and styling her hair.

"Do you understand your purpose?" Said Skorr.

She nodded. "Ready to advance the great Sontaran cause sir."

"Then get to work."

"Ok. You two, with me." She led the Grey and Harris out and back up the stairs.

Fortunately, they'd abandoned the jeep not far from the Nobles' house. The Doctor knocked hard on the door, before Donna arrived. "You would not believe the day I'm having."

The Doctor got down on the ground to have a look at the ATMOS box on the exhaust of Sylvia Noble's car. He then opened up the bonnet to have a look at the components within the engine itself. Donna, meanwhile, was dialling her phone.

"Should I requisition us a vehicle sir?" Said Ross.

The Doctor nodded. "Anything without ATMOS. And don't point your gun at people."

Ross went off to find one. He'd had no intention of taking it at gunpoint anyway.

"Is it him?" Said Wilf's voice. "Is it the Doctor?" He rushed over and came to a halt. "It's you!"

"What?" The Doctor glanced over and abruptly did a double take as he saw the man he'd last seen manning a newspaper stall on Christmas Eve, when the rest of London had evacuated the city. "It's you!"

"What, you've met before?" Said Donna.

"Yeah, Christmas Eve. He vanished right in front of me." Said Wilf

"And you never said?"

"Well you never said!" He turned back to the Doctor. "Wilf, sir, Wilfred Mott. You must be one of them aliens?"

"Well, yeah, but don't shout it out." The Doctor grinned, and shook his hand. "Nice to meet you properly Wilf."

"Wow, an alien hand."

"Is anyone answering?" The Doctor asked Donna.

"It's just ringing. What is it son-ta-rons?"

"Son-tar-ons. They're behind ATMOS. But remote controlling cars isn't enough. There must be something more to it." If they planned to invade, disrupting the enemy's transport networks would certainly help. But a race with spaceships already had a stronger transport system anyway.

Finally, Martha's voice came on the phone. "Don't tell me. Donna Noble."

The Doctor took it off her. "Martha, it's the Sontarans. They're in the factory. Tell Colonel Mace code red Sontaran. They should be in the files. But if they meet them, tell them not to start shooting. UNIT will get massacred. You got all that?"

"Code red Sontaran." Martha nodded. "Gotcha." And she rang off.

"Doctor Jones?" Mace found her at this point. "Found anything?"

"Nothing to report." She said.

Mace nodded and left.

"You tried sonicing it before." Said Donna, as the Doctor tried again.

"Yes' but now that I know it's Sontaran, I know what I'm looking for."

"The thing is, Doctor," said Wilf, "Donna's my only grandchild. I want you to promise me you'll take care of her."

"She takes care of me."

"Ah, that's my girl. She was always bossing people about. Even when she was a baby. Our little general, we used to call her. And then she got older and she was bringing the boys back. A different one every week."

"Don't start." Donna sighed.

"'ere, who was that posh one, with the nail varnish."

"His name was Chris. He lives in Kilburn now… with a man."

"Ah!" The Doctor cried suddenly. "It's a temporal pocket!" A brief flash passed over the box and a collection of little nozzles appeared. "Just a second out of sync with real time. I knew there was something else hidden inside."

"I don't know, men and their cars. Sometimes I wish I were a car." Sylvia approached, but she too halted when she saw the Doctor. "Oh, it's you! Doctor… whatever you said your name was."

"Yep, that's me." Said the Doctor, without looking up from his sonicing.

"What, have you met him too?" Said Wilf.

"Dad, it's the man from the wedding! When you were laid up with Spanish flu. I'm warning you. Last time that man turned up, it was a disaster."

As if ATMOS had a sense of irony, the nozzles all spat out a cloud of white smoke, sending them scurrying away.

"A converter had been activated." Said a technician.

"What?" Cried Staal. "Show me where!"

The technician brought up a map.

"London." Said Luke. "That's Chiswick."

"Who can have such knowledge?" Said the tech.

"Only the Doctor!" Cried Staal. "So he survives! Very well. He will choke to death along with the humans. Soldiers, we move to the final phase. We move to war. Prepare for the subjugation of earth!"

Seconds later, a stream of dozens of fully armed Sontaran infantry came marching out and towards the teleport in neat formation.

"Trigger the converters!" Shouted Staal. "And deadlock every single one!"

The Doctor, meanwhile, deactivated the ATMOS device and waved away the cloud of smoke that surrounded the engine. "There, that should stop it."

"What did I tell you!" Shouted Sylvia. "He's blown up the car! What sort of Doctor blows up cars?"

"Oh, not now mum." Donna sighed.

"I should have made an appointment!" Her mother stormed away.

The Doctor, meanwhile was sniffing the air. "That wasn't just exhaust fumes, there was something toxic in that gas."

"What so like poison gas? But if they've got toxic gas on every car on Earth…" Donna looked up and down the street, where two or three cars were parked outside every house, each with a sticker in the window, announcing that they had ATMOS installed.

"It's not safe. I'll get it off the street." Said Wilf, climbing into the car.

"No!" Shouted the Doctor, but too late. At that exact moment, the Sontarans' activation signal came through. The doors locked and the engine roared into life.

"Granddad get out of there!" Shouted Donna. "Turn it off!"

"I can't, I didn't turn it on!" Shouted Wilf, holding up the keys.

The Doctor tried to deactivate the converter again, but it wouldn't work this time. Nor would the door locks.

It wasn't just on Donna's street. A cloud of thick white smoke poured out of half the cars in the world. Anyone stood nearby was quickly engulfed in the chocking gas, which rapidly radiated outwards, filling whole streets and whole car parks.

In the ATMOS factory, Colonel Mace hurried down to the main entrance hall, where the handful of jeeps they'd parked inside were also pouring out gas. "Turn them off!" He shouted. "Turn all of them off!"

"We can't sir. Something's controlling them!" Shouted a Corporal. "It's every car on the planet!"

"Well find a way!"

Several soldiers at this point, tried to shut down the engines by shooting at them, something that was difficult to do since military vehicles are designed to withstand a certain amount of bullet damage. Others just scrambled for cover.

Only one figure remained calm. Martha strolled through the area, looking around with a sense of satisfaction. The plan was underway successfully. Time for her to get to work.

The Doctor physically ripped some cables from the ATMOS box and went to see if that had helped. But the doors were still locked.

"There's gas in the car!" Donna screamed, while her mother watched in horror from the doorway. "He'd gonna choke!"

The Doctor returned to the engine and tried even more furiously to find something that wasn't deadlocked. It was only now that he got a good look down the street at the lines of cars that were producing the gas, and the rapidly thickening smog.

"Four million weapons." Staal said triumphantly. "Sontar ha. Sontar ha!" He punched his palm with his fist as he chanted. "Sontar ha! Sontar ha!"

Luke watched as every Sontaran on the bridge joined in with his routine. "Sontar ha! Sontar ha! Sontar ha!" Correctly guessing this was some sort of war dance, he joined in. "Sontar ha! Sontar ha! Sontar ha! Sontar ha! Sontar ha!" They chanted triumphantly as the humans chocked below.