Thanks again to Bonnie for beta reading! BBC owns everything.

And thanks so much to the people who review...y'all don't know how much I appreciate it :)

In truth, leaving Rose alone with Sarah Jane was probably not the best of the Doctor's plans. Certainly they were both intelligent, competent galactic-travellers capable of accomplishing amazing tasks – but he failed to account for another trait they both shared: they were both women.

"Rose," Sarah Jane leaned over a desk as the younger girl attacked a computer with the Doctor's borrowed sonic screwdriver. "Can I give you a bit of advice?"

"I've got a feeling you're about to," Rose didn't look at her, but did come out from beneath the table.

"I know how intense a relationship with the Doctor can be," she tried. "I don't want you to feel like I'm intruding."

"You're not," Rose answered shortly. Sarah Jane blinked. "I'm not threatened or nothin', if that's what you think."

"Right, good," Sarah Jane nodded. "Because I'm not interested in picking up where we left off."

"No?" Rose folded her arms suspiciously. "With the big sad eyes and the robot dog? Either you were tryin' to get a ticket back on the TARDIS or you just like to hurt him, either way you want a slap."

"I would never hurt him!" Sarah Jane stiffened. "Do you think you're the only person who has cared about him?"

"Of course not, even Jack -" she cut herself off and pursed her lips angrily. "I don't expect any sort of label, but him an' me, we're special."

"You must be blind," Sarah Jane looked down her nose at the young woman. "The Doctor is many things, but a love interest is not on his list. He'll do the same to you as he did me."

"He's already done it!" Rose's hand were planted firmly on her hips. "He sent me home before, an' I found a way back; fact is he knows that I'm not gonna just sit home and be a good girl because space stuff is too hard!"

"Excuse me, I have no problem with space stuff!" Sarah Jane's eyes widened angrily. "I saw things you wouldn't believe!"

Rose narrowed her eyes. "Try me."

"Mummies."

"I've met ghosts."

"Robots. Lots of robots."

"Slitheen, in Downing Street."

"Daleks!" Sarah Jane spat out.

Rose snorted. "Met the Emperor!"

"Anti-matter monsters."

"Gas-mask zombies."

"Real living dinosaurs!"

"Real living werewolf!"

"The Loch Ness Monster!"

Rose stopped short, eyes widening. "What, seriously?"

Sarah Jane sagged against the desk, laughing slightly. "Oh, no," she shook her head.

Rose softened slightly. "Guess I'm not as different as I thought. Still act like a junior school girl when it comes to men." Sarah Jane nodded slowly, still chuckling quietly to herself. Rose bit her lower lip and leaned forward. "What was he like when you knew him? Was he still sad?"

Sarah Jane paused and nodded slowly. "In a different way," she acknowledged. "He didn't fit in with his people, I suppose that was why he spent so much time on Earth, even before the Time Lords exiled him here. I admit, I still miss my first Doctor more than anything...he was so debonair, so charming. A bit grandfather-ish toward me, but so kind. The second one paid a good deal less attention to his surroundings, I think so much of his mind was focused on not tripping over the scarf he wore that he didn't manage to see anything else."

"What d'you mean, first and second?" Rose's brow furrowed in confusion. Sarah Jane stiffened.

"You mean he hasn't told you about regeneration?" she gasped. "You've been together this long and he didn't warn you?"

Rose frowned, eyes wide. "What's regeneration?"

Sarah Jane let out a deep breath. "Oh, Rose, I shouldn't have – the Doctor treasures his secrets, you know that."

"Yeah, an' it's important enough that you assumed I'd know," Rose held her ground. "What is it?"

"You will have to ask him," Sarah Jane replied firmly. She took a deep breath and smiled. "Does he still spend all his time tinkering under the console?"

Rose nodded with a hesitant chuckle. "Yeah, he does," she paused and chewed her bottom lip. "With you, did he call you a stupid ape any time you disagreed with him, even if it was over somethin' totally valid, like his cooking?"

"Well, not in so many words," Sarah Jane shook her head thoughtfully. "But he would sometimes spend hours wondering how we had managed to descend from the trees in evolutionary standards."

"Oh, he does that too!" Rose giggled.

Sarah Jane smiled mischievously. "And does he still stroke bits of the TARDIS?"

"Yeah! Yeah, he does!" She laughed in earnest now. "An' I'm like, 'do you two want to be alone?'"

"Yes!" Sarah Jane let out a guffaw, which set Rose off further.

"Got anything yet?" They both turned, still laughing – they hadn't even heard the Doctor approach. He frowned at them. "What's wrong with you two?"

Rose pointed the sonic screwdriver at him and laughed harder. He glanced between them.

"Right," he turned on his heel and went back the way he'd entered – the sound of their hysterics following him. He muttered a few unflattering things about humanity as he left. "Should've stuck to robot dogs."

The computers came alive suddenly, without warning. Green images, geometric patterns and foreign letters flashed too quickly to read.

Rose and Sarah Jane exchanged looks as the Doctor adjusted something on a terminal far away from their teasing laughter.

"You wanted the program, well there it is," Sarah Jane called over to him.

The Doctor looked up sharply and his face set into hard lines. "It's a code," he muttered, furrowing his brow. He lifted a hand and pointed at certain aspects of it, pausing thoughtfully. He jolted, eyes wide. "No. Oh, no, no, no, no, no!"

"What is it?" Sarah Jane asked, shooting a worried glance toward the screen.

"They're not writing a code, they're trying to crack it," he began to pace. "Everything is science, Sarah, you know that! Even matter, life itself is an equation. The Skasis Paradigm is the equation that life is based on, the universe itself. They'd have control over everything. They'd be gods."

Behind them, Rose leaned against a row of tables, looking pale and faintly ill. She averted her eyes from the monitors.

"Why humans though, why children?" Sarah Jane persisted.

"They need the creativity, the energy," he was getting angrier, his voice rising as he solved the quandary. "The only thing humans haven't got enough of is brainpower, so they use the oil. Greases the brain, makes it run faster. They force-feed it through the chips until they're clever enough and then use them."

"Let the lesson begin," the smooth, cultured voice of Brother Lassar interrupted their discussion. The Doctor turned, already angry. "Think of it, Doctor; with the Paradigm solved, reality becomes clay in our hands. We can shape the universe and improve it."

"The universe as perfected by the Krillitanes? No thanks, I don't think the Beatles would perform good bat sonar."

"You act like such a radical, and yet all you want to do is preserve the old order. Think of the changes that could be made if this power was used for good."

"By you?" The Doctor scoffed. "Think I'm better off old fashioned."

"No, Doctor, by you," Lassar slunk forward. "The Paradigm gives us power, but you could give us wisdom. Become a God at my side. Imagine what you could do; think of the civilizations you could save. Perganon; Assinta... your own people, Doctor. Standing tall. The Time Lords... reborn."

Rose bowed her head, covering her ears; Sarah Jane was already shaking her head. "Doctor, don't listen to him," she pleaded quietly.

"And you could be with him throughout eternity," Lassar continued, his eyes focused on Sarah Jane. "Young... fresh... never wither, never age... never die. Their lives are so fleeting. So many goodbyes. How lonely you must be, Doctor. Join us."

The Doctor took a deep breath and met the gaze of the Krillitane. "I've said before, Mr. Finch, I'd make a terrible god." There was a short pause, and then he picked up a chair, throwing it through the large display screen.

Lassar ducked, covering his head as the glass shattered; the Doctor ran past, Sarah Jane at his heels and Rose a few feet behind.

A horrible scream erupted from the disguised Krillitane, and throughout the school they could hear echoing cries from the others.

Mickey, and inexplicably, a young boy, were running through the halls. The small group congregated at the stairs, freezing for just a moment as the Krillitanes crawled along the walls toward them.

"Right then, run!" The Doctor took off in the opposite direction, grabbing Rose's hand and pulling her rather roughly after him.

Hiding in the canteen was apparently not a good plan – the doors locked behind them, leaving them quite unfortunately trapped in a large room with highly carnivorous aliens.

Sarah Jane found herself quite comfortable in the familiar situation of fearing for her life and did her best to dodge the creatures.

The Doctor brandished a chair like a weapon, swinging it at the aliens who swooped down toward his companions. Rose slid under a table, covering her head with her hands and kicking at any Krillitanes who dared come near her.

A sudden flash of red garnered the attention of everyone – human, Krillitane and Time Lord – as a laser cut through one of the bat-like creatures whom the Doctor had previously been fighting off with his chair.

"K-9!" Sarah Jane cried, almost moving toward him before she had to duck again from one of the teachers-cum-aliens.

"Suggest you engage running mode, Mistress!" The robot dog called out to her.

"Right!" The Doctor threw the chair at one of the bats and ran for one of the doors, waving the others on to follow. "Come on, you lot, you heard the dog!"

"Maximum defense mode!" K-9 continued to shoot at the Krillitanes, distracting them well enough to allow the humans – and Time Lord – to escape.

Their destination ended up being in the opposite side of the building, in the little office where Rose had taken temporary residence. The small group crouched behind the counter, to avoid being seen through the window of the door.

"Right then, what do we know?" The Doctor was all business.

"Bats," the boy Mickey had saved – Kenny, by name – supplied.

"Krillitanes," Sarah Jane corrected. "Aliens that look like bats because they absorbed the DNA of bat-people."

"They eat rats," Rose added, resting her forehead against her knees. "Wouldn't be surprised if they ate the missin' kids."

"The other teachers've all gone," Mickey pointed out, glancing around the office. "An' the staff. Either they was all aliens or they got eaten too."

"Wouldn't bet on a whole school of them, it'd be impossible to switch the entire staff," the Doctor frowned. "Come on, more information!"

"They absorb DNA," Sarah Jane said slowly. The Doctor nodded irritably, gesturing for her to continue. She glanced at him. "How?"

He blinked. A slow grin spread across his face and he reached across to kiss her firmly on the forehead. "Sarah Jane Smith, I knew you were brilliant! Yes!"

"What?" Kenny glanced between them. "What's that mean?"

"It means," the Doctor fiddled with his screwdriver. "Rose, give me your mobile," she started, shook her head and handed it over; he opened the back and began to tinker with it. "It means that once I've used Rose's mobile to call K-9, we can use the sample of Krillitane oil," he pulled the jar from his pocket with a grin, before handing it to Mickey and adjusting the mobile with his screwdriver, "to get a lock on their DNA. And, if I'm very clever – which I am – I can use it against them."

"Wow," Kenny breathed.

The Doctor pressed a series of keys on Rose's phone and hit send. He grinned, and then tossed the device to Mickey. "That should do it," he informed them all, clearly pleased with himself.

"So," Mickey frowned. "How you gonna use it against 'em exactly?"

"Ah," the Doctor paused. "Well, that's complicated, you wouldn't understand."

"Which means he hasn't figured it out yet," Rose muttered, head still pressed against her knees.

"Oi, that's not at all true. I've figured out half a dozen ways, just haven't decided which one yet."

"And at least one of them is likely to work, is it?" Sarah Jane hid a smile.

"Should just build m'self a new dog for company," he muttered to himself. "Ungrateful apes."

There was a soft thumping on the door; the Doctor jumped to his feet and peered through the little window. "Oh, K-9!" He opened it just enough to allow the metal dog and quickly sealed it with the screwdriver. He ducked back behind the counter, summoning K-9 after him. "Got to find a way to loosen the bond to the Krillitanes' absorbed DNA. Any thoughts?"

"Affirmative."

He grinned. "Knew I programmed you well. Go on then."

"Sonic pulse, Master. With correct frequencies, Krillitanes will be unable to maintain a shape."

The Doctor waved a hand dismissively. "Don't have the parts, thought of that already."

"You have the parts, Master."

There was a long pause as everyone glanced to the robot. Sarah Jane was already shaking her head. "No, K-9, you can't! I need you!"

"No alternative, Mistress. I will complete the analysis of the Krillitane oil. Master will then complete a pulse cannon."

"Doctor, don't you dare!"

He couldn't meet her eyes. "He's right, there are no other options."

Sarah Jane let out a half-choked sob as the Doctor began to quietly trade information with K-9 via the sonic screwdriver. She fell back and hugged her knees, refusing to watch as the metal casing was slowly taken apart and the Doctor began to remove components.

He let out a soft sigh and rubbed the metal head gently. "Good dog," he murmured quietly.

"Affirmative."

"Oh, K-9," Sarah Jane whispered. "I'm so sorry."

"Safety of Mistress is pre-programmed as first priority. Quickly, Master!"

The Doctor nodded, and with a quick intake of breath pulled apart a long red wire. The remaining power quickly faded, dimming all of his lights and stilling his movements. Rose wrapped an arm around Sarah Jane, letting the older woman cry into her shoulder. She closed her eyes and leaned her head against the counter, a frown etching deep lines into her pretty face.

Other than Sarah Jane's slowly quieting tears, the room was silent while the Doctor worked.

"I'll have to get them together," the Doctor said suddenly some minutes later. They all raised their heads, staring. "When I say, you run and get out."

Rose lifted her head, staring at him. "You gone mad? I'm not gonna leave you."

"Rose, there's no time to argue," he narrowed his eyes. "Not tryin' to kill myself, I'll get out but I can't be worried about you lot."

"I'll make sure she gets out," Mickey interrupted quietly. Rose turned, frowning at him. "Just shut up and do as someone says for once, okay?"

She blinked, then scowled. The Doctor's eyebrows shot toward his hairline, but he nodded slowly. "Yes...that. Ricky, you've had an intelligent thought, congratulations!" He grinned. "Now luckily you've taken responsibility for Rose, which means if she gets hurt I get to take it out on you. Best avoid that!"

"As if you've gotta threaten me to take care of Rose," Mickey grunted. "I'll watch out for Ms. Smith here too."

"Well, that's been a lovely jolt of testosterone," Sarah Jane gave them both flat looks. "But since I believe Rose and I are more than capable of taking care of ourselves, why doesn't everyone else simply worry about getting their own hides out before we all die?"

"I'm game," Kenny grinned at her. She smiled back and ruffled his hair gently.

"Good," she turned to the Doctor expectantly. "Any recommendations for the best route out of here?"

"Back stairs are just to the left," Rose had once again rested her head against the back of the counter, but she raised her arm and pointed. "The wall Mickey drove your car through isn't far from the bottom."

"Yeah, that'll do," the Doctor grinned. "Ten minutes after I leave, you run. Don't worry 'bout me – just get out. Trust me."

"Right," Sarah Jane nodded severely. "As you say, Doctor."

He watched them for a few spare heartbeats – more of his than theirs put together, though there was no need for them to think about such things – and stood. "Ten minutes," he reminded them. They all nodded and he grinned once more before picking up the sonic cannon, the sacrificed remains of a beloved friend, and running for the door.

"Anyone got a watch?" Kenny asked suddenly. The adults paused, glancing at one another.

Rose sighed and pushed herself to her knees, reaching for Mickey's front pocket. He objected for half a moment, then her mobile appeared in her hand. She waggled it silently and he grinned sheepishly. Nine minutes and thirty-seven seconds later, they ran for the door.

Students were pouring out of the computer labs, racing through the halls toward the hole provided by Sarah Jane's car. The small party slid into the river of children, following them into the cool air outside.

Two minutes after that, a dull whoop reverberated out from the school, shattering every window. The crowd gaped. Then the creaking began. Bricks slid from their designated location – pillars were collapsing. Mere moments after the whoop, there was a deafening roar and sudden crash as the centre of the building collapsed in on itself, tugging the remaining walls down in a domino effect. The children began to cheer, chanting proudly when Kenny proclaimed a part in it.

Rose and Sarah Jane stared in horror at the remains of the building. They leaned on one another, too stunned to do anything other than watch and pray for movement from within the rubble.

"He wasn't," Rose started.

"No, it's impossible," Sarah Jane agreed.

"Nothin's impossible," the girls stiffened and turned slowly. The Doctor smirked at their dazed expressions. "Little faith, please? I tell you to trust me an' this is what I get?"

Rose took a step forward, paused, and then ran full-tilt toward him. She pitched herself into his arms, trying desperately not to cry. "You always gotta blow somethin' up!" she complained when she could speak again.

"I blame the films," he informed her seriously. She glanced up and he grinned, hugging her tighter for just a moment before he pulled back – though he kept one arm firmly about her waist. "Tea?"

Sarah Jane and Mickey exchanged glances. "Doctor?" she questioned after a moment.

He tilted his head toward a small copse of trees at the edge of the property – under which sat a familiar blue box. "Landed a couple minutes before I left, wanted to see the results! Couldn't properly enjoy the subtlety of the explosions when I was runnin' for me life now could I?"

"You think you're so Bond," Rose teased.

"In more ways than you realize," Sarah Jane muttered. The Doctor shot her a sharp glance, but she only smiled. "I would love to come in, Doctor."

He beamed and the little group headed for the safety and comfort of the TARDIS.

Sarah Jane ran her hand gently along the rail even as her eyes widened. She stared up at the high ceilings and cobbled-together console. "You've redecorated!"

"Couple o' times," the Doctor agreed. "Like it?"

"Oh, oh, I do!" she stroked one of the coral struts lightly. "I preferred it...as it was, but it'll do."

Rose sat on the rail, resting her forehead against the coral. "I love it," she murmured.

Sarah Jane frowned slightly and moved closer. Her voice lowered gently. "Are you all right?"

"Just a headache," Rose smiled weakly. Sarah Jane reached out and tucked an errant strand of golden hair back behind her ear. "'M fine."

"You're very strong," she agreed quietly. "You're good for him. Just remember...to look me up, someday." The details of 'someday' were left unsaid. "If you need to."

"I will," Rose bit her bottom lip. "You could..." she glanced at the Doctor, and raised her voice. "Doctor?"

He looked up from the console with a mad grin. "You know there's a lovely planet in the Kuixlin galaxy, has the best auroras in the universe. It's just the right time of year for a good look at 'em. Sarah?"

"This is a time machine, Doctor," Sarah Jane reminded him fondly. "It's always the right time of year in the TARDIS." She took a deep breath. "But...I can't do it any more."

His smile faded, but he nodded. "You've got a life to lead, Sarah."

She smiled wider, in response. "Yes, I really do." She took a deep breath and said a silent goodbye to someone else she had long missed...and felt the gentle hum under her fingers increase. She nodded to the others and followed the Doctor to the door – not remotely surprised to see that they had moved across town while she spoke to Rose.

"It's daft. But I haven't ever thanked you for that time and...I wouldn't have missed it for the world."

He leaned against the closed doors, observing her. "Not a bad story for the memoirs?"

"Oh, I think so," she smiled to herself. "I could make a fortune in true fiction."

He laughed and nodded. "Exactly."

She took a deep breath and released it slowly. "Goodbye, Doctor."

"Don't be daft, it's not -"

"Please," she interrupted. "Please, say it this time."

He smiled slowly. "Goodbye," there was a pause, he grinned widely and swept her into a hug. "My Sarah Jane!" She laughed as he swung her lightly, and then suddenly he was gone, dashing back to the TARDIS.

She didn't look back until the achingly familiar sound of dematerialisation had faded. When she turned the ship was gone, as she'd known it would be. Her face lit up when she saw what remained.

"K-9! But, but you were blown up!"

"Mistress!" K-9 Mark IV trundled to her side. "Master rebuilt me. My systems are much improved with new undetectable hyperlink facilities."

"Oh!" she crouched down beside him, stroking his head. "He replaced you with a brand new model!"

"Affirmative!"

She smiled sadly. "He does that. Come on, you. Home. We've got work to do."

"Mistress, I also have a message from Master!"

"Oh?" She crouched again, curious. A panel slid open and a small lipstick tube appeared with a sticky note attached. She picked it up and began to laugh. 'Sonic lipstick,' the note read. 'Harry shouldn't want one, but if he does I'm blaming you. Take care of K-9 -- The Doctor'

"Can I talk to you for a minute?"

Rose sighed, but followed Mickey out into the familiar yard of the Powell Estate. "What's wrong?"

"Let me see your mobile," he asked quickly. She frowned but fished it out of her pocket, handing it over. He pressed a few keys and handed it back. Her brow furrowed.

"What'd you do?"

"Deleted my number," he admitted, shoving his hands in his pockets. He waited to be shouted at, but when he looked up he only saw stunned disbelief on her face. "I get it, I do. I ain't ever gonna be like him. It's good you found somethin' better, but I won't sit around waitin' on you to call 'cause you're stoppin' by for a haircut and want whatever it is you want from me. An' I can't not do it until I know for sure you ain't callin'."

"Mickey," she bit her lip, and he tried to pretend that there was something other than guilt in her tone.

"Your mum knows how to get me if you end up stayin' someday," he said suddenly. "But next time you're just visitin', I don't want to know. An'...yeah. That's it then."

"I'm sorry," she whispered. "I really am."

"Yeah, I know," he sighed and pulled her close for a hug. "Bye, Rose."

"Bye, Mickey," she leaned against the TARDIS as she watched him walk away. She reached back and opened the door, stumbling a little as it gave way behind her.

The Doctor quirked an eyebrow toward her, but she shook her head and crossed to the corridor. Sleep sounded nice...sleep sounded fantastic actually.

Maybe then her head would stop throbbing.