The Doctor pulled all the connections he could find in the engine, but the gas continued to fill the car.
“Get me out of here!” Wilf begged before collapsing.
“Doctor!” Donna yelled.
Lilith swore in Gallifreyan.
“He's going to choke. Doctor!” Donna panicked.
“It won't open!” the Doctor shouted when the sonic screwdriver did nothing.
“Move over!” Lilith pulled out her blaster and shot the windshield, shattering the glass. “Come one, get him out.”
The pulled Wilf out of the car and led him a safe distance away. “Thanks.”
Sylvia stared at Lilith. “What kind of a gun is that?”
“51st century sonic blaster,” she answered, holstering the weapon. “Handy when breaking glass from the 21st.”
“Get inside the house. Just try and close off the doors and windows,” the Doctor ordered.
Jenkins is drove over in a black cab. “Doctor, this is all I could find that hasn't got ATMOS.”
“Donna, you coming?” Lilith asked.
Donna nodded. “Yeah.”
“Donna. Don't go,” Sylvia begged. “Look what happens every time that Doctor appears. Stay with us, please.”
“You go, my darling,” Wilf insisted. “Don't listen to her. You go with the Doctor and his girl. That's my Donna.”
“If it makes you feel any better,” Lilith said as they drove away to the industrial estate, “She’s reacting better than my grandmother.”
“How did your grandmum react?”
“She slapped him. Hard.”
When they reached the estate, they all got out of the cab. “Ross, look after yourself. Get inside the building.”
“Will do. Greyhound Forty to Trap One. I have just returned the Doctor to base safe and sound. Over,” he said into the walkie-talkie.
“The air is disgusting,” Donna coughed.
“It's not so bad for Lilith and I. Go on, get inside the TARDIS. Oh, I've never given you a key.” He reached into his pocket and pulled one out. “Keep that. Go on, that's yours. Quite a big moment really.”
Donna rolled her eyes. “Yeah, maybe we can get sentimental after the world's finished choking to death.”
“Good idea.” The Doctor grabbed Lilith’s hand and ran toward HQ.
“Where are you going?” Donna called
“To stop a war,” Lilith called back. “What else?”
The Doctor dragged Lilith into HQ and warned Colonel Mace not to engage the Sontarans. The plan was to take the TARDIS and get on board their ship. Lilith and Martha followed the Doctor back to where they had left the TARDIS. Lilith wrinkled her nose.
‘There’s something wrong with Martha,’ the Doctor thought to her.
‘Tell me about it. She reeks of clone,’ Lilith responded.
‘We’ll figure it out when we get back to the TARDIS.’ The TARDIS, as it so happened, was not where they left it.
Martha looked around. “But where's the TARDIS?”
“Taste that, in the air,” the Doctor said, sticking his tongue out.
“You mean aside from all this damned gas? It’s teleport exchange. Blech."
“It's the Sontarans. They've taken it,” the Doctor concluded. “We’re stuck on Earth like, like an ordinary person. Like a human. How rubbish is that? Sorry, no offence, Martha, but come on.”
“So what do we do?” Martha asked.
Lilith frowned. “The TARDIS is shielded. They shouldn’t have been able detect it.” She looked at Martha.
She stared back, not blinking. “What?”
“Nothing, just wondering, have you called Tom? Or your family?"
“No. What for?”
“The gas. Tell them to stay inside.”
Martha finally blinked. “Course I will, yeah but what about Donna? I mean, where's she?”
“Oh, she's gone home,” the Doctor said, dismissively. “She's not like you. She's not a soldier. Right. So. Avanti!”
‘Martha would’ve noticed. That one’s definitely a clone. So the question is, where’s the real Martha?’
Lilith muttered a swear in Gallifreyan as they ran back to HQ.
“Change of plan,” the Doctor said to Mace.
Mace nodded. “Good to have you fighting alongside us, Doctor.”
“I'm not fighting. 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 said. “It's harmful, but not lethal until it reaches eighty percent density. We're having the first reports of deaths from the center of Tokyo City.”
“Jodrell Bank's traced a signal, Doctor,” said Mace. “Coming from five thousand miles above the Earth. We're guessing that's what triggered the cars.”
Lilith scowled. “The Sontaran ship.”
“NATO has gone to Defcon One. We're preparing a strike.”
“You can't do that,” the Doctor protested. “Nuclear missiles won't even scratch the surface. Let me talk to the Sontarans.”
“You're not authorized to speak on behalf of the Earth,” argued Mace.
The Doctor glared at him. “I've got that authority. I earned that a long time ago.” He stuck the screwdriver into the communications system. “Calling the Sontaran Command Ship under jurisdiction two of the Intergalactic Rules of Engagement. This is the Doctor."
And image of Staal appeared on the screen. “Doctor, breathing your last?”
“My God,” Mace breathed, “they're like trolls.”
Lilith shook her head. “Loving the diplomacy there, Colonel.”
The Doctor ignored them both. “So, tell me, General Staal, since when did you lot become cowards?”
“How dare you!” Staal exclaimed. “Doctor, you impugn my honor!”
“Yeah, I'm really glad you didn't say belittle, because then I'd have a field day,” the Doctor said. “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. Where's the fight in that? Where's the honor? Or are you lot planning something else, because this isn't normal Sontaran warfare. What are you lot up to?”
“A general would be unwise to reveal his strategy to the opposing forces.”
“Ah! The war's not going so well, then. Losing, are we?”
“Such a suggestion is impossible!” Staal scoffed.
“What war?” Mace asked.
“The war between the Sontarans and the Rutans,” Lilith explained. “It's been going on for a good fifty thousand years. Fifty thousand years of death for no reason.”
“For victory! Sontar-ha! Sontar-ha! Sontar-ha!” all the Sontarans started chanting.
The Doctor rolled his eyes. “Give me a break.” He changed channels with the screwdriver to a cartoon.
“Doctor. I would seriously recommend that this dialogue be handled by official Earth representation,” Mace insisted.
The Doctor switched it back to the Sontarans. “Finished?”
“You will not be so quick to ridicule when you'll see our prize. Behold!” It was the TARDIS. “We are the first Sontarans in history to capture a TARDIS.”
Lilith noticed the look on the Doctor’s face. He had a plan. “Well, as prizes go, that's 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,” said Staal.
“Big mistake though, showing it to me. Because I've got remote control.”
“Cease transmission!” the Sontaran ordered. The screen went black.
The Doctor shrugged. “Ah, well.”
“That achieved nothing,” Mace snapped.
“Oh, you'd be surprised.”
‘Planning on sharing with the class?’
‘If Donna doesn’t phone soon, you phone her. I’ll tell you when.’
Martha held up a clipboard. “There’s carbon monoxide, hydrocarbons, nitrogen oxides, but ten percent unidentified. Some sort of artificial heavy element we can't trace. You ever seen anything like it?”
The Doctor snatched it out of her hands. “It must be something the Sontarans invented. This isn't just poison. They need this gas for something else. What could that be? Lilith?”
“Only ever seen Sontarans once, with you and Rose on Sontar. Well, aside from Strax, but I don’t think he really counts.”
“Launch grid online and active,” someone announced.
“Positions, ladies and gentlemen, Defcon One initiatives in progress,” Mace said.
“What?” the Doctor demanded. “I told you not to launch.”
“The gas is at sixty percent density. Eighty percent and people start dying, Doctor. We've got no choice.”
One of the techs started the count down. “Launching in sixty, 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 shouted. “For once, I hope the Sontarans are ahead of you.”
“North America, online. 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, four, three, two, one, zero.”
Nothing happened; the world map went blank. “What is it? What happened? Did we launch? Well, did we?”
“Negative, sir,” the tech said. “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 wondered, looking closely at Martha. “Any ideas?”
“How should I know?” She sounded a bit defensive.
‘I really don’t like this.’
‘You and me both.’
“Greyhound Forty declaring absolute emergency. Sontarans within factory grounds. East corridor, grid six,” came Ross’s voice from the Colonel’s communications device.
“Absolute emergency. Declaring Code Red. All troops, Code Red,” Mace responded.
“Get them out of there,” the Doctor hissed.
Mace looked at him, debating, and clearly decided to ignore him. “All troops, open fire.”
Lilith heard the sound of gunfire and, a split second later, the sound of humans shouting as they died. “Guns aren't working. Inform all troops, standard weapons do not work,” Ross reported. “Tell the Doctor it's that cordolaine signal. He's the only one who can stop them.”
“Greyhound Forty, report. Over,” said Mace. “Greyhound Forty, report.” Nothing. Just static. “Greyhound Forty, report.”
“He wasn't Greyhound Forty. His name was Ross,” the Doctor said, darkly. “Now listen to me, and get them out of there!”
Mace gulped. “Trap One to all stations. Retreat. Order imperative. Immediate retreat.”
It was no use; the attack was a massacre.
“They've taken the factory.”
“Why? They don't need it. Why attack now? What are they up to?” The Doctor paced back at forth. “Times like this, I could do with the Brigadier. No offence.”
“Launch grid back online,” the tech told them. The grid flickered to life, but went blank again. “They're inside the system, sir. It's coming from within UNIT itself.”
“Trace it,” Mace ordered. “Find out where it's coming from, and quickly. Gas levels?”
“Sixty six percent in major population areas, and rising.”
Lilith stormed into a nearby room to take a few deep breaths. It seemed to be Colonel Mace’s office, as he and the Doctor entered a moment later.
“Why are they defending the factory only after we were inside?” Mace asked.
“Because they wanted UNIT here, the Doctor said. “You gave them something they needed. Something now hidden inside the factory. Something precious.”
“We've got to recover it. This cordolaine signal thing, how does it work?”
“It's the bullets,” Lilith explained. “It causes expansion of the copper shell.”
“Excellent. I'm on it.” Mace got up and left.
“For the billionth time, you can't fight Sontarans!” the Doctor yelled after him.
Lilith’s phone rang. She answered. “Donna, thank Rassilon. Here’s Dad.” She handed the Doctor the phone.
“What's happened? Where are you?” Donna asked.
“Still on Earth,” the Doctor answered. “But don't worry; I've got my secret weapon.”
Lilith heard Donna groan. “Oh. Somehow that's not making me happy. Can't you just zap us down to Earth with that remote thing?”
“Yeah, I haven't got a remote, though I really should,” the Doctor admitted. “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. But they'll all be on battle stations right now. 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.”
Pause. “What do you need me to do?”
Lilith took the phone back. “The Sontarans are inside the factory, that means they've got a teleport link with the ship. They’ll have deadlocked it by now so we need you to reopen the link.”
“But I can't even mend a fuse,” Donna protested.
“Donna, trust me. You can do this, I promise.”
“There's a Sonterun. Sontaran,” she said.
“Did he see you?”
“No, he's got his back to me.”
Lilith let out the breath she was holding. “Right, okay. Listen, on the back of his neck, on his collar, there's a sort of plug, like a hole. It’s called the Probic vent. One blow to the Probic vent knocks them out.”
She could practically hear Donna frowning. “But he's going to kill me.”
“I'm sorry. I swear I'm so sorry, but you've got to try. You can do this."
She heard Donna walk across the grating in the console room, then her footsteps outside the ship. Then she heard a clang and a grunt and the sound of a Sontaran collapsing to the floor. “Back of the neck.”
The Doctor snatched the phone. “Now then, you got to find the external junction feed to the teleport.”
“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 F’s back to back.”
“Well, there's a door.” Donna’s voice was starting to shake.
“Should be a switch by the side.”
“Yeah there is. But it's Sontaran shaped, you need three fingers.”
Lilith face palmed. “Donna, you've got three fingers.”
“Oh, yeah.” A door slid open. “I'm through. Right. T with a line through it.”
Colonel Mace reappeared talking to the techs. “Got to go. Keep the line open.” He handed the phone back to Lilith, then proceeded to shout at Mace. “I said, you don't stand a chance.”
“Positions. That means everyone.” Mace tossed gas masks to Lilith and the Doctor.
“You're not going without me,” Martha said.
Lilith forced a believable grin. “Wouldn't dream of it, come on.”