The Doctor checked the map he took from the guard. “Wait. This is it, the hidden tunnel. There must be a control panel.”
“It's another one of those numbers,” Donna said, seeing another plaque. “They're everywhere.”
“The original builders probably left them. Some old cataloguing system, maybe?” Lilith guessed.
“You got a pen? Bit of paper?” Lilith reached into her transdimensional pockets and pulled out a notepad and a pencil and gave it to Donna. “Because, do you see, the numbers are counting down. This one ends in one four. The prison cell said one six.”
“Always thinking, all of you. Who are you people?” Jenny asked.
“I told you," the Doctor said, sonicing the wall, “I'm the Doctor.”
“The Doctor. That's it?”
Donna shrugged. “That's all he ever says.”
Lilith defended him. “That’s all that matters.”
“So, you don't have a name either? Are you an anomaly, too?”
“No,” the Doctor snapped.
“Oh, come off it,” Donna scoffed. “You're the most anomalous bloke I've ever met. “
The Doctor got into the control panel. “Here it is.”
“And the Gallifreyans, the Time Lords, what are they for, exactly?” Jenny questioned.
“For?” He frowned. “They're not, they're not for anything.”
“So what do you do?”
“I travel through time and space.”
“He saves planets,” Donna added, “rescues civilizations, defeats terrible creatures. And runs a lot.”
Lilith nodded. “She’s not joking, there's a ridiculous amount of running involved.”
The door opened. “Got it!” the Doctor cheered. Cobb’s voice came from somewhere nearby. “Now, what were you saying about running?”
They sprinted down the revealed passageway, only stopping when they reached an array of laser beams crisscrossing the passage.
“That's not mood lighting, is it?”
The Doctor tossed the clockwork mouse into the lasers. It got disintegrated.
“No, I didn't think so,” Donna sighed.
“Arming device,” the Doctor muttered. He worked on a blue box nearby.
“Donna.” Lilith waved her over to check out another set of numbers.
She added them to the list. “Always eight numbers, counting down the closer we get.”
“Right, here we go,” the Doctor announced. “We’d better be quick.”
Cobb’s voice was coming closer.
“The General.” Jenny started back.
The Doctor stopped her. “Where are you going?”
“I can hold them up.”
“No, we don't need any more dead.”
“But it's them or us.”
“It doesn't mean you have to kill them,” the Doctor said.
“I'm trying to save your life,” Jenny insisted.
“Listen to me. The killing. After a while, it infects you. And once it does, you're never rid of it.”
Jenny looked at him somberly. “We don't have a choice.”
“Jen,” Lilith said, gently, “there’s always a choice.”
Jenny shook her head. “I'm sorry.”
Jenny ran around the corner and the Doctor watched her go. “I told you. Nothing but a soldier.” He went back to the blue box.
Lilith glared at him “She's trying to help.” She turned back to where the sound of gunfire was coming from. “Jenny, come on!”
“I'm coming!” she called back.
The lasers went out. “That's it.”
“Jen, leave it! Let's go!”
The Doctor and Donna ran down the corridor, the former dragging Lilith behind him. “Jenny, come on!” Jenny ran around the corner. “That's it.”
The lasers reappeared and the blonde skidded to a stop. Lilith swore in Gallifryean.
“No, no, no, no, no, no. The circuit's looped back,” the Doctor hissed.
“Zap it back again,” Donna suggested.
“The controls are back there.”
“They're coming!” Jenny shouted.
“Wait! Just… there isn't…” He looked around, desperately. “Jenny, I can't!”
“I'll have to manage on my own.” Jenny tossed the gun away. “Watch and learn, Father.” She took a step back and launched herself forward, flipping her way through the laser beams like something out of a spy movie.
Donna gaped at her. “No way. But that was impossible.”
“Not impossible. Just a bit unlikely.” The Doctor grinned at Jenny. “Brilliant! You were brilliant. Brilliant.”
Lilith hugged her sister tightly. “That was freaking epic, Jen.”
“I didn't kill him,” Jenny said. “General Cobb, I could have killed him but I didn't. You were right. I had a choice.”
Cobb and the soldiers appeared at the other side of the lasers. The three girls ran.
Once they made it a safe distance away and the Doctor had caught up, they slowed to a walk. “So, you travel together, but you're not together?” Jenny asked Donna. Lilith laughed.
“What? No. No. No way,” Donna denied. “No, no, we're friends, that's all. I mean, we're not even the same species. There's probably laws against it.”
Lilith shrugged. “Mom’s human. Well, sort of. Don’t tell Dad, though.”
“And what's it like, the travelling?” Jenny asked before Donna could question the ‘sort of’.
“Oh, never a dull moment.” Donna grinned. “It can be terrifying, brilliant and funny, sometimes all at the same time. I've seen some amazing things though. Whole new worlds.”
“Oh, I'd love to see new worlds,” Jenny said, dreamily.
Lilith put her arm around her. “You will. Won't she, Dad?”
He looked back. “I suppose so.”
Jenny’s eyes went wide. “You mean. You mean you'll take me with you?”
“Well, we can't leave you here, can we?”
“Oh, thank you, thank you, thank you!” She hugged the Doctor. “Come on, let's get a move on.” She and Lilith ran ahead.
“You said our mum is human,” Jenny said once Donna and the Doctor were out of earshot. “Where is she?”
Lilith bit her lip. “Well, she’s not our mom yet. I’m from the future, see. And in the future he married our mom and they have me, then Kel, then the twins. So technically right now, you’re my younger sister, but in the eventually, you’ll be my older sister.”
Jenny frowned. “That’s a bit confusing.”
“Tell me about it. But that has to be a secret, Dad can’t know about his future.”
She nodded. Gunfire echoed down the corridor. The two girls looked at each other, then raced back. “They've blasted through the beams. Time to run again.” Jenny grinned. “Love the running, yeah?”
The Doctor beamed. “Love the running.” They came to a dead end. “Can’t be. This must be the temple. This is a door.” He started sonicing the wall.
There was another plaque with numbers on it. “And again,” Donna said. “We're down to one two now. These can't be a cataloguing system.”
“I've got it!” the Doctor shouted.
“I can hear them,” Jenny warned him.
“They're getting closer.”
“Now! Got it.” The Doctor got the plain door open and they go through.
Jenny was last. “They're coming. Close the door.” The Doctor locked the door. “Oh, that was close.”
“No fun otherwise.”
Donna looked around. “It's not what I'd call a temple.”
Jenny frowned. “It looks more like…”
“Fusion drive transport,” the Doctor finished. “It's a spaceship.”
Lilith furrowed her eyebrows. “The original one? The one that the first colonists came in?”
The Doctor shrugged. “Well, it could be, but the power cells would have run down after all that time. This one's still powered-up and functioning. Come on.”
They headed up a flight of stairs to see someone is cutting their way through another door. “It's the Hath,” Jenny said. “That door's not going to last much longer. And if General Cobb gets through down there, war's going to break out.”
The Doctor spotted a screen. “Look, look, look, look, look. Ship's log.” The screen said, ‘Messaline Leader One mission log designation XG2482942-372.’ “First wave of human/Hath co-colonization of planet Messaline,” he read.
“So it is the original ship,” Jenny concluded.
“What happened?” Donna asked.
“Phase one, construction,” the Doctor answered. “They used robot drones to build the city.”
“But does it mention the war?”
The Doctor scrolled down through Phase One in progress. Lilith pointed to the bottom of the screen. “There, final entry. Mission commander dead. Still no agreement on who should assume leadership. Hath and humans have divided into factions.”
She looked at the others. “That must be it. A power struggle. The crew divided into two groups, one for each species, and turned on each other. They started using the progenation machines, and suddenly you've got two armies fighting a never ending war.”
“Two armies who are now both outside,” Jenny pointed out.
“Look at that,” Donna said. The number 60120724 was on a display above a screen showing the whole planet. “I spent six months working as a temp in Hounslow Library, and I mastered the Dewey Decimal System in two days flat. I'm good with numbers. It's staring us in the face.”
“What is?” Jenny questioned.
“It's the date. Assuming the first two numbers are some big old space date, then you've got year, month, day. It's the other way round, like it is in America.”
Lilith’s eyes widened. “It’s the New Byzantine Calendar!”
“The codes are completion dates for each section,” Donna explained. “They finish it, they stamp the date on. So the numbers aren't counting down, they're going out from here, day by day, as the city got built.”
The Doctor grinned. “Yes. Oh, good work, Donna.”
“Yeah. But you're still not getting it. The first number I saw back there, was sixty twelve oh seven seventeen. Well, look at the date today.”
“Oh seven twenty four…” He trailed off. “No.”
Jenny looked at the numbers, confused. “What does it mean?”
“Seven days,” Lilith said. “That's it. Seven days.”
“What do you mean, seven days?
“Seven days since war broke out,” the Doctor said.
“This war started seven days ago. Just a week. A week!” Donna exclaimed.
That confused Jenny even more. “They said years.”
“No, they said generations,” Lilith corrected. “And if they're all like you, then they're products of the progenation machines.”
“They could have twenty generations in a day,” the Doctor added. “Each generation gets killed in the war, passes on the legend. Oh, Donna, you're a genius.”
“But all the buildings, the encampments, they're in ruins,” Jenny said.
“No, they're not ruined. They're just empty. Waiting to be populated. Oh, they've mythologized their entire history. The Source must be part of that too. Come on.”
Further along the, Martha turned a corner and saw them. “Doctor!”
The Doctor hugged her. “Oh, I should have known you wouldn't stay away from the excitement.”
“Aunt Martha! Are you okay?” Lilith asked, hugging her too.
Then it was Donna’s turn. “Oh, you're filthy. What happened?”
“I, er, took the surface route,” Martha admitted.
“Positions,” Cobb’s voice echoed down the halls.
“That's the General. We haven't got much time, ” the Doctor said.
“We don't even know what we're looking for,” Donna pointed out.
Martha sniffed the air. “Is it me, or can you smell flowers?”
“Yes,” the Doctor agreed. “Bougainvillea. I say we follow our nose.”
They came to an area in the spaceship filled with plants. The Doctor spun around, taking everything in. “Oh, yes. Yes. Isn't this brilliant?”
They walked up to a glowing globe on a pedestal with wires running to it. There was a control panel and screen nearby. “Is that the Source?” Donna asked.
“It's beautiful,” Jenny breathed.
“What is it?”
“Terraforming,” Lilith said. “It's a third generation terraforming device.”
Donna looked around. “So why are we suddenly in Kew Gardens?”
“Because that's what it does. All this, only bigger, much bigger,” the Doctor explained. “It's in a transit state. Producing all this must help keep it stable before they finally—” The Hath and the soldiers ran in from opposite sides. “Stop! Hold your fire!”
“What is this, some kind of trap?” Cobb demanded.
“You said you wanted this war over,” the Doctor said to him.
“I want this war won.”
“You can't win. No one can. You don't even know why you're here. Your whole history, it's just Chinese whispers, getting more distorted the more it's passed on. This is the Source. This is what you're fighting over. A device to rejuvenate a planet's ecosystem. It's nothing mystical. It's from a laboratory, not some creator. It's a bubble of gases. A cocktail of stuff for accelerated evolution. Methane, hydrogen, ammonia, amino acids, proteins, nucleic acids. It's used to make barren planets habitable. Look around you. It's not for killing; it's bringing life. If you allow it, it can lift you out of these dark tunnels and into the bright, bright sunlight. No more fighting, no more killing.”
The Doctor picked up the terraforming device. “I'm the Doctor, and I declare this war is over.” He threw it on the floor, where it smashed and released gas and energy. Everyone watches it slowly rise up, then they start to put down their weapons. All except Cobb.
“What's happening?” Jenny asked.
“The gases will escape and trigger the terraforming process,” Lilith told her.
“What does that mean?”
Lilith beamed. “It means a new world.” Jenny laughed with delight.
Both of the girls noticed Cobb shifting his aim to the Doctor, but Jenny was slightly quicker. “No!”
She jumped in front of her father and the bullet pierced her chest. The Doctor and Lilith caught her before she could collapse and they laid her on the ground, the Doctor taking her into his lap.
Lilith gripped her arm. “Jenny? Jen. Talk to me, Jen.”
Martha knelt down next to them to check the wound.
“Is she going to be all right?” Donna choked.
Martha shook her head without a word.
“A new world,” Jenny whispered. “It's beautiful.”
“Jen, be strong now. You need to hold on, do you hear me?” Lilith begged.
The Doctor held her tighter. “We've got things to do. You, me, and Lilith, hey? Hey? We can go anywhere. Everywhere. You choose.”
“That sounds good,” she managed.
“You're my daughter, and we've only just got started. You're going to be great. You're going to be more than great. You're going to be amazing. You hear me? Jenny?”
Jenny closed her eyes. Lilith broke into tears.
“Two hearts. Two hearts. She's like me. If we wait. If we just wait…” the Doctor said, voice thick with desperation. He looked up at Martha, begging her to confirm.
“There's no sign, Doctor. There is no regeneration. She's like you, but maybe not enough.”
“No,” he rasped. “Too much. That's the truth of it. She was too much like me.”
The Doctor kissed Jenny’s forehead and gave her to Lilith, then went over to Cobb. Cline and another soldier held his arms and made him kneel. The Doctor picked up the pistol and pointed it at Cobb's head.
Donna and Martha watched him worriedly for a few moments before he put the safety back on. “I never would. Have you got that? I never would. When you start this new world, this world of human and Hath, remember that. Make the foundation of this society a man who never would.” He started to walk away.
Lilith didn’t move.
“Lilith, we have to go,” the Doctor said.
“Five and a half hours,” she whispered, hoarsely.
“Mom says to always wait five and a half hours. I have my vortex manipulator, I’ll meet you back at the TARDIS.”
Donna knelt next to her. “Lilith—”
“She’s a part my family,” Lilith snapped. “We always wait. Let me do this.”
The other ginger stood and walked away with Martha and the Doctor just as sunlight began to stream through the stained glass windows. Lilith held her sister tightly. “Come on, Jen. Wake up.”
Five and a half hours later for her, but a few minutes for the others, Lilith appeared outside the TARDIS.
“Well?” Martha asked.
Lilith bit her lip. “She wasn’t meant to travel with Donna, Dad, and I.”
The four of them walked into the TARDIS and the ship dematerialized, leaving Messaline behind.