The Doctor, coughing, soniced the air vents in the launch control room. They'd only just managed to make it in here before the Commander had sealed the doors shut with heavy bulkheads.

The moment they entered, they found the room strewn with dead bodies.

The air in the room was filled with smoke and poison gas.

"Don't breathe it in," the Doctor warned the two kids. "Breathe through a cloth."

Imula and Cariolo grabbed the bottom of their shirts, and used them as a filter. Imula fell into a coughing fit.

The Doctor was using his respiratory bypass system to great advantage.

"What happened?!" Cariolo cried. His eyes were fixed on the victims, lying dead on the floor.

"Someone killed them all," said the Doctor, as he managed to get the air vents to pump out the bad air and pump in fresh air. "There. Should be back to normal, shortly."

He turned to the Commander, who was coughing like crazy.

"Sorry, Commander, but I'll have to stop you launching that missile," said the Doctor. He grabbed the man, dragged him away from the controls. "It's really rather important for the future of this planet."

Cariolo looked like he was going to be sick, as he stared at all the dead bodies around him. He staggered over to the control console, nearer to the Doctor. Reached out, grabbing the edge for support, as he wavered and tried not to hurl.

"I must obey my orders," said the Commander, still in a monotone. "I must obey!"

"But you'll kill the world!" Imula said, her coughs dying down. Then, to the Doctor, "Why don't you just use that watch thing on him? Like you did on Cariolo?"

"Oh, I doubt it'd work," the Doctor replied, as the Commander's struggles died away, and he drifted into a listless trance. "This mind control even got into my head — and that means it's too strong to be counteracted by a mere fobwatch." He reflected. "Thing is… I've felt exactly this same type of hypnosis, before. It was an ability that used to belong to — what did she call them? Oh, yes. The Riashta Horrin."

Cariolo jumped, at the name.

"Oh, look at that," the Doctor said. "I think you've just given yourself away, Cariolo."

Imula frowned, confused. "But… that's just Cariolo. My big brother."

"Oh, no, it's not," said the Doctor. "In fact, he's not even a 'he', at all." He turned Cariolo around, so the 'boy' faced him, head on. "Don't get me wrong, she's quite the little actress. But she's always taps your shoulder in one specific spot, Imula, just before you act erratically. She suggested hiding inside my TARDIS — like she knew it was more than just a box. Keeps picking my sonic out of my pocket when she thinks I haven't noticed — then replacing it, before I need it, again. Asks questions that are just a little too pointed and on target, pretends to be sick so she can press all kinds of buttons. Besides which, her face is too feminine, and her body… well, it's a bit curvy, don't you think?" The Doctor shrugged. "Her recovery from the hypnosis was the final clincher. Definitely pretending."

"Doctor, what are you talking about?" Cariolo said. "I'm me! Tell him, Imula! I just want to help you! I just want…"

Then, in a flash, all traces of caring or compassion faded from Cariolo's face.

"Ah, screw it," Cariolo said, now in a girl's voice, turning to the control panel and activating the launch. "I was sick of this, anyways."

The Doctor lunged to stop her, but Cariolo shoved him out of the way — with a strength that surprised the Doctor.

Cariolo grabbed a metal rod from the base of a chair, yanked it free. "Don't touch the control panel, Doctor," the now-clearly-female Cariolo threatened. "Or you're dead." She spun around, to face Imula. "Just like this little crybaby."

Then, she plunged the metal rod through Imula's chest.

"No!" the Doctor said, trying to intercept her.

But the Commander, suddenly back in Cariolo's power, grabbed the Doctor by the arms and held him fast.

"Car…iol…?" Imula managed to wheeze.

"Yeah, stop talking, now," Cariolo said, shoving the metal rod through Imula's head. "You're really starting to bug me."

A cracking sound tore through the air, as the metal rod split the bone.

And, with a small sob, little Imula died.

"What did you do that for?" the Doctor demanded. "That little girl did nothing to you! She trusted you."

"So?" Cariolo shrugged. "What do I care? The more they trust, the easier they are to kill." She glanced back at the equipment, behind her. "Wish I'd fed on the brat, but… you know. The heat. Bad for the launch machinery."

"So you just killed her," the Doctor said, fiddling with his sonic screwdriver, behind his back. Taking care to make sure the Commander — still restraining him — couldn't tell what he was doing. "No reason. Just… killed her."

Cariolo shrugged. "She deserved it. Everyone always does."

"And that's what you believe?" The Doctor raised his voice, a little, in righteous indignation — to mask his buzzing the control panel with his sonic screwdriver. "Someday, you'll hate yourself for doing this, you know."

"As if." Cariolo stalked towards him, licking her lips. "But, tell me, Doctor. What are you? There's so much time on you, it's like you've taken a bath in it and little droplets keep dripping off your skin, every time you move." Her eyes looked hungry. "That rich juiciness of eons and eons, mixed with artron. I can almost taste it."

"Yes, you've said that to me, before," the Doctor said. "Except, last time, you seemed embarrassed."

Cariolo's hunger flickered, a hair. Replaced with suspicion. "What do you mean?"

"Let's just say… this isn't the first time we've met," said the Doctor, "and it won't be the last. I've met you, both in your past — and in your future."

And the strangest thing about that was… the Seo he met with Narvin still hadn't known who he was.

"You're quite different, in your own past and future," the Doctor observed. Taking in her deep brown hair, her facial features not yet altered by nano-surgery. "You even look different. But you're still bold, clever, and manipulative — I can see that in all of you."

"Now I know you're lying," said Cariolo. "My past is gone. And I don't have a future." Something died, in her eyes, as she said it. "There's nothing for me, in the future. Just this. Forever."

"Your father was a Tevin," the Doctor prompted. He thought back to that little girl, wandering around in the velvet grass of an alien world. "He used to send you away, telling you he had 'company'. You thought it was someone's name. Mr. Company."

Cariolo paused.

"And you had a rather neat trick you could do, back then," the Doctor continued. "When you got scared… you melted into the shadows."

"How do you know about that?" Cariolo demanded.

"Oh, because I know you," the Doctor said. "I said that, didn't I? I know all about those injections you got, when you were young. All about the Daleks. All about your father. And all about what we saw when we hid together, under the windowsill, and listened in."

The name 'Dalek' seemed to mean nothing to Cariolo.

In fact, she appeared to have no memory of any of her last encounter with the Doctor.

"You know me," Cariolo said, just checking to verify. "You met me, before my father died. I… introduced myself to you?"

"You…" the Doctor started. Then stopped.

Realized where she was going with this.

"I told you my name?" Cariolo asked. "My birth name?"

"No," the Doctor said, quickly.

"Liar." She picked up the metal rod, again. "I was going to save you for dessert… but if you know enough to sign my Writ of Erasure, then you're way too dangerous to live." She gave a cruel smile. "Goodbye, Doctor. Thanks for helping me destroy this planet."

But before she could make her move, a high-pitch feedback sound whined through the Commander's walky-talky.

Cariolo cringed, hesitating for just a second.

The bulkhead swished open. And Seo raced in, armed with a very large, very lethal-looking gun.

"Seo!" the Doctor cried, with a grin. Then, glancing at Cariolo, dropped the grin, and added, hurriedly, "Don't come in!"

"I think it's way too late for that," said Seo. She stepped directly in between Cariolo and the Doctor. Pointed the gun at Cariolo. "You locked the missile launch into place. Undo it. Or you die."

Cariolo grabbed the walky-talky from the Commander, and crushed it underfoot. Then snarled at Seo.

"Seo," the Doctor said, softly. "Put the gun down. This isn't going to help."

"You must be the Doctor's 'friend'," said Cariolo. "So… what? You know me, too?"

Seo met her eyes, steadily.

"Yes," Seo said, her voice so quiet, it was almost inaudible. "I know you. I know you better than anyone else alive." She swallowed, hard. "You're what I hate most. The thing I can't destroy. The thing I can't take back." She stared at her, the hints of tears in her eyes. "I know you. So well. And, somehow, I have to live with that."

Cariolo hesitated, before killing Seo.

As if something… were stopping her.

"Now, shut down that launch," Seo said, pointing the gun in her face. "Or, I swear, I will kill you."

Looking at her, the Doctor was afraid she really might do it, too.

That was a paradox he definitely didn't want to deal with.

"Oh, you want me to disable the launch?" Cariolo asked, heading over to the control panel. "I guess you're a little out of the loop. The Doctor already sabotaged the control panel with his sonic thingy. That's why he had to keep talking so loud, while he was doing it."

Seo blinked. "What?"

"Oh, yeah — I figured that out, way back," Cariolo said. She glanced at the Doctor. "I was gonna let it go. You know. Let him feel like he was winning. Toy with him, a bit, before I tore him to shreds. I mean — he is fun, isn't he?"

"That's how you see him?" Seo said, her hands shaking with fury. "Some kind of… toy, for your amusement?"

"Isn't everyone?" Cariolo shrugged. "Well. Whatever. Now that I know the Doctor's too dangerous to live…" She hit a few switches, undoing the sabotage. "…I dunno… it's just no fun, playing with him."

"No, don't…!" Seo stepped forwards, as if to grab Cariolo and drag her away. But froze. Stopped herself.

"Seo," the Doctor warned.

Cariolo examined her, more carefully. "You know, I take it back," she said. "Maybe I should keep him alive. After all — there's something really weird about you two." She pointed at the Doctor. "He feels sorry for me. You can see it all over his face." She turned to Seo. "But you… I think you seriously hate me." She spread her arms open. "And yet… you don't kill me. You can't even get up the courage to lay a finger on me. Not even if I do something like this."

Screams came from everywhere, around the base. The army personnel burst into golden ribbons of time, their bodies melting under the drainage.

Even the Commander collapsed to the ground, twitching, as the life was drained out of him.

"Stop it!" Seo screamed, lunging at her.

The Doctor had to grab Seo and pull her back, forcibly. "You know you can't touch her." He wrestled the gun out of Seo's hands. "And you definitely can't shoot her. Remember who she is!"

"Remember who I am?" Cariolo asked, as she finished feeding on the personnel of the army base. "That's a weird thing to say. Who am I, to you?"

Seo's eyes were fixed on the control panel, behind Cariolo. It had melted, beneath the heat. "You fused the controls."

"Yeah, I do stuff like that." Cariolo stepped closer to Seo, and the Doctor dragged Seo back, even further. "You've got about a minute left to live. So… go on. Who am I, to you?"

"You wouldn't believe me if I told you," Seo said.

"Oh, yeah?" said Cariolo. "Try me."

Seo said nothing.

Her eyes were fixed on the control panel.

"Fine, whatever!" said Cariolo, and turned her gaze on the Doctor.

The Doctor bent double, as sudden pain flared through his head. Seo caught him, wrapping her arms around him.

"Doctor?!" Seo cried. Then, looking at Cariolo, "You did this."

Cariolo shrugged. "Tell me, or I make the Doctor's brain go squish."

Seo looked like she wanted to punch her hand straight through the wall.

"What the hell is wrong with the universe?!" Seo snapped. "Is there some memo I missed, telling everyone to try to kill the Doctor for no good reason? I mean, geeze! Leave the poor guy alone!"

"Then tell me," said Cariolo. "Who are you?"

"Who am I?!" Seo thudded her hands against her chest. "Just look at me! Who do you think I am?!"

Cariolo's grip over the Doctor's mind suddenly vanished.

She stared at Seo, not even able to speak.

Seo, instead, ignored her and turned back to the Doctor. "Are you okay?"

"Fine, fine," the Doctor dismissed. His eyes fixed on the control panel. "But we have to find a way to abort that launch."

"Don't worry about it," Seo said, as the countdown neared its conclusion. "Already done."

The Doctor turned back to her. "What, really?"

"You don't honestly think I missed that you sabotaged the control panel?" Seo sighed. "Come on, Doctor. I'm not that stupid. I just figured that she…" Nodding at Cariolo, "…would figure out your sabotage, and counteract it."

"What are you talking about?" Cariolo asked.

Seo laughed. "Really? You don't know?"

As the countdown reached zero, a huge indicator above the control panel flashed, "Abort, abort, abort."

"I figured out about the Doctor's sabotage, remotely, before I entered this room," Seo said. "I went to the secondary control room. Took advantage of his sabotage, and remotely deactivated this control room, so I could switch to the secondary one. Then I locked the controls to auto-abort at the last second." She smiled. "Only thing left for me to do, was to keep you in here, distracted, until the countdown ended."

Cariolo jumped to her feet. "Secondary control room. Fine. Whatever! I'll go there, then."

"You don't get it, do you?" Seo shook her head. "You drained everyone on this base. Even the people in the secondary control room. The heat in there will have done exactly the same thing to that console as it did to this one. Fused the controls. And General Halwather's team is already releasing a chemical to decontaminate the air and water."

Cariolo froze.

"Which, to summarize, means… I've just changed a fixed point in time," Seo said. "This planet was doomed to die… and I just saved it!" She couldn't help but beam at the Doctor, at this. "And you thought your people hated me, before! Just think about the looks on their faces, when they see this!"

"Clever, bold, and lacking basic sense," the Doctor sighed. "Yes, those are definitely traits I see in both of you."

Seo laughed.

Cariolo just stood there. Fixed to the spot. No expression on her face.

"Oh, come now, Cariolo," said the Doctor. "Don't look so glum. Things get better for you, you know. I've seen your future."

"Don't call me 'Cariolo'," said Cariolo. "It's not my name." Her eyes remained fixed on Seo. "You know it's not my name, don't you?"

"What do you prefer? 'Puppy'?" Seo was in too good a mood to let this get to her. She felt a little giddy, in fact.

Cariolo bristled. "You gave me my name," she said. "You should know it."

"I…" Seo frowned. She had given herself a name — Seosyrae. But how would this younger-her know that? "How could you possibly know…?"

"You're supposed to be dead," said Cariolo. "The Shadow said so. He was very clear about it."

Seo's eyes went wide. "Oh. Oh, no."

"What?" said the Doctor.

"The Shadow!" Seo said. "Why didn't I think of that? He's here, on this planet. He must be."

Seo jumped to her feet.

"We've got to go," Seo told the Doctor, grabbing him by the hand and hauling him up. "Evacuate everyone. Once the Shadow sees what's happened, here, he'll send in the whole vampire army to wipe the planet out."

"No clues, no survivors," Cariolo agreed. "That's the Shadow's rule." She shrugged. "Except… sometimes, I like to keep a few treats to play with and eat, later. Keep them canned up and ready."

In a flash, Cariolo head-butted the Doctor into the far wall, grabbed the sonic screwdriver off him, and dashed outside. With a buzz of the sonic, the bulkheads slammed shut.

Seo ran to the bulkhead, trying to beat her younger-self to it, but arrived a split second too late. She thudded her hands down against it. But it was sealed fast.

"Canned up and ready," Seo repeated. "Damn her!" She spun back around to the Doctor. "We've got to get out of here. Sooner or later, she's going to come back for us… and you don't want to know what she'll do, then."

The Doctor caught his breath. "I take it this means you've reconsidered flouting the Laws of Time and altering your own past?"

"Well, it was fun, back when I could remember everything that happened and use it to my advantage," Seo said. She held her head in her hands. "But then… I guess I changed too much. Now, I can't remember a thing about any of this."

"Yep, that's what happens when you muck about with your own past," the Doctor said. "Who's this 'Shadow' person, by the way? Or can I guess?"

Seo frowned. "Guess? What do you mean, guess?"

"Oh, only that — turning into a shadow is something you used to be able to do," the Doctor pointed out. "And considering where all your abilities wound up… I'm guessing your sire earned the name 'the Shadow' by using that particular ability to his great advantage. Hiding in shadows, then gobbling people up."

Seo stared at the Doctor.

Lost for words.

"You really don't remember me, do you?" the Doctor asked. "I know that your doubling back on your own timeline would be enough to scramble your memories from around now, but… my entering your early childhood should have made some impression, at least."

"You entered my early childhood?" Seo said.

The Doctor shrugged. "It seems that, when I touched your hand, the Gem of Braxiatel interacted with the TARDIS and launched me back into your own past. All the way back to when you were a very little girl." He leaned against the melted control console. "Incidentally, your real name is very pretty."

Seo's face went even paler than it had been, before. "You know my…?"

"Of course — you told it to me," said the Doctor. Then, just to prove he really had been there, he repeated the name back to her.

Seo swore beneath her breath. "Doctor, if you tell anyone," she warned, "you've signed my death warrant."

She paused.

Then, drooping a little, added, "Although, to be fair… by sending you back into my past… I've already signed yours."

The Doctor frowned. "I'm sorry?"

"Nothing," Seo assured him. "Don't worry about it. Whatever happened, I'll undo it. Promise." She buried her face in her hands, taking slow, deep breaths. "Somehow."

The Doctor nodded. Thinking. "That Tevin came back, didn't he? The one who wants to kill me?"

Seo said nothing.

"And he told you something about where he got his marching orders from," the Doctor guessed. No surprises, there — Seo's father must have figured out that the Doctor had overheard their plans. "What else did the Tevin tell you? Did he mention your father and the Daleks?"

Seo shot her head up. "What?!"

"Ah," said the Doctor. "Or, perhaps… not."

"What do you mean, my father and Daleks?" Seo said. She stared at the Doctor, rising fear on her face. "Doctor, what did you see, in my past? What did you do to make my father hate you?"

The Doctor opened his mouth.

Then hesitated.

Remembered the kind, loving father, from Seo's memories. The one who loved Seo, and would never think of harming her, in any way.

Remembered the real father, scheming with the Daleks to experiment on his own daughter, callously discussing the death of Gallifrey, covering up for the Daleks, as they exterminated anyone who came too close.

What had Narvin told her? Don't ask too many questions.

"Doctor," Seo said, stepping towards him. "What did my father have to do with the Daleks?"

"What? Oh," the Doctor said. "Yes. Right." And, on the spot, came up with a lie. "The Daleks kidnapped you. As a baby. Your father rescued you from them."

Seo looked the Doctor over, carefully. "My father… rescued me? From the Daleks?"

"Absolutely," the Doctor said.

Seo said nothing for a long moment. Then, with a small smile, said, "It's very sweet of you to lie to me, like that."

The Doctor grimaced. "Ah."

"My father was a coward, Doctor," Seo explained. "I remember." She shrugged. "If I really was captured by Daleks, and you really were in my past… it's pretty obvious who actually did the rescuing."

The Doctor said nothing.

"Thank you, Doctor," Seo said.

Again, the Doctor said nothing. Instead, just turned his attention to the bulkheads, and trying to find a way out of this control room.

"No good," the Doctor said. "Deadlocked."

"They would be," Seo replied, heading over to the control console, to see if there was anything inside that she could use to help them both. "I wasn't stupid. Not even back then."

The Doctor began trying to change around the wiring inside the wall. "You know, I can tell that you're the same person. In some ways, you're absolutely the same. Of course, in others, you're completely different — but, still."

Seo hesitated. Then tried something on the control panel, to limited success. "Is that an insult or a compliment?"

"Just an observation," the Doctor said. "When is this, in your… her… timeline? During the Olitzitz War?"

Seo shook her head. "Oh, no. After. Long after. I was never this bad, during the war. I actually hesitated before killing small children, back then."

The Doctor pried open a second panel, on the wall.

"No, this is shortly before I killed all the other vampires and ran away," Seo said. "I remember — I was at my worst, at this point." She thought back. Tried to remember what was happening, at this point in her life. "The Shadow was always off, trying to find victims to sire. I mean, we'd lost so many vampires, during the war. We started at over five hundred, and wound up with… less than fifty… by the end."

The Doctor whistled.

"So… yeah," said Seo. "The Shadow was usually away, instead of hanging around to watch my back. The other vampires really hated how he gave me special treatment, all the time. So they waited until he was gone. And then… hurt me."

"I'm sorry." The Doctor realized he was getting nowhere with wall panel number two, and moved on to wall panel number three.

"Vyroneka was the worst," said Seo. "She was the Shadow's girlfriend. Any time she got angry at him, she took it out on me. Back before the war, the Shadow killed anyone who laid a hand on me — besides himself, of course. But after…"

"…with fewer than fifty vampires left," the Doctor concluded, "he couldn't afford to lose anyone."

"Exactly." A small smile spread across Seo's face. "Vyroneka. I really enjoyed killing her. The way she writhed and screamed, before I…!"

The Doctor shot Seo a hard look.

"Not that I find murder fun, now, I mean," Seo amended, quickly. "Just… for her… back then…"

The Doctor sighed. "As I said. Sometimes, I really can tell that you're the same person." He tried rewiring panel number three, again. Then, frustrated, tried just kicking the bulkhead.

But, of course, all that did was give him a stubbed toe.

"I could have told you that wouldn't work," Seo said. She rushed over, handed him some electronic gizmos. "Here. Use these."

"They're broken," the Doctor observed. "Useless."

"For electrical energy," Seo qualified. She raised up one of the pieces. "But it's perfectly set up to harness the angular momentum of an electron's spin. You know. Spintronics. And the best thing about spintronics is that it operates like electricity — but has the added bonus of conducting through an electrical insulator." She clanged her fist against the bulkhead door. "Like the insulator keeping this bulkhead shut."

The Doctor grinned. "Brilliant!" He began wiring those pieces in, as well. "You know, you really are clever. Almost as clever as me, come to think of it."

"Why, thank you, oh superior lifeform," Seo said, dryly.

The Doctor, however, clearly hadn't seen this as any sort of insult. "No, really. You are." He reached for another component. "Hasn't Narvin ever told you so?"

Seo laughed. "Narvin vacillates between sweet-caring-and-huggable, and arrogant-Time-Lord-you-just-want-to-slap. Sometimes, he tells me I'm a suicidal, senseless idiot. At other times, he says I'm staggeringly brilliant."

Her laughter died away.

And, for a moment, she just stood there. A component in her hand, unable to do anything except stare at it.

"Narvin," she repeated. Her voice very far away. "He told me… not to ask questions. And he tried to stop me leaving my ship behind, at the Dalek base."

The Doctor said nothing.

"The Daleks did something to me, when I was very young, didn't they?" Seo asked. "Something I don't remember. But, whatever it was… Narvin knows about it."

"Seo," the Doctor sighed.

"Maybe he even had a hand in it," Seo realized. She realized she was starting to hyperventilate, at the idea. "You don't think… he was involved in my childhood? You don't think… our whole relationship was just a charade, so he could keep tabs on me for some CIA project?"

"Seo," the Doctor said.

Seo looked up at him.

"You know Narvin better than I do," the Doctor said. "But I'll tell you that, when Narvin went looking for you in that Dalek base, and thought something might have happened to you… he wasn't just worried. He was terrified. And when he believed you were dead… he just about broke down. Wanted to murder all the Daleks that had done that to you. I had to work hard, to stop his grief from starting a war."

The hints of tears appeared in Seo's eyes.

"And, I'll tell you, for nothing," the Doctor said, "that if any harm comes to you, while I'm around — I know Narvin will skin me alive."

The Doctor turned back to the door controls. Suddenly, got a flash of inspiration. He grabbed the component out of Seo's hand, made a few small tweaks to it, then shoved it inside.

The deadlock clicked.

And unlocked.

"Ha!" the Doctor said. "Look at that!"

Seo gave a sigh of relief. "Thank the universe." She rushed outside. "We've got to evacuate all the people on this planet, before…"

The Doctor caught her by the arm. "This is a fixed point in time. Remember? I'd say the best thing, now… is to get you back to the TARDIS."

"I've been to this planet, in the future," Seo said. "No one survives. The whole planet is dead." She gritted her teeth. "And if I leave… then that's what I'm allowing to happen. That's what I'm doing to them."

"The longer you stay here, the greater the odds of you giving Blinovitch a run for his money," the Doctor pointed out. "Or haven't you considered what would happen, if younger-you decided to drain all the temporal energy out of older-you?"

Seo hadn't.

The thought semi-terrified her.

"All that time energy you've drained, Blinovitching over and over again," the Doctor went on. "Colliding and smashing apart — inside you, inside the time vortex, inside…"

"You've made your point, Doctor," Seo said. And, with a heavy sigh, gave in. "Maybe I can't take back my past, after all. Maybe that whole offer was a lie from the very start."

"Sorry… offer?"

Seo didn't explain. "Let's just… get out of here. Save President Romana. Stop the Daleks."

"That's the spirit," the Doctor said — although he couldn't help but get the nagging suspicion… that this was where the Daleks had wanted them, all along. "To the TARDIS!"