Note: this story begins during "Boom Town", during the run of the Ninth Doctor. It also begins at the beginning of The Lightning Thief. And obviously, I own neither of these universes. The first chapter is all Doctor Who exposition. Percy Jackson fans, stick with us. Allons-y!

Cardiff.
Twenty-first Century.
A Blue Box, the time-travelling TaRDiS, sits in the middle of a plaza. Ten seconds ago, the night was calm and cool. Now, the ground shakes and lightning pours from the TaRDiS and the sky has a tear in the very fabric of space itself.

"What the hell are you doing?" yelled the Doctor as he ran into the TaRDiS, dragging Margaret, a plump, middle-aged alien behind him. The Doctor had shaved brown hair and wore both a leather jacket and a panicked expression. The TaRDiS was flashing, emergency sirens were going off, and sparks flew every direction.

"It just went crazy!" shouted Captain Harkness amid bursts of sparks and flame. He looked up from where he was desperately trying to fix a jerry-rigged tribophysical waveform macro-kinetic extrapolator.

The Doctor ran to the control panel in the center of the room. "It's the Dimensional Rift! Time and Space are ripping apart! The whole city's gonna disappear!"

Captain Jack banged a console and yelled, "It's the extrapolator! I disconnected it but it's still feeding off the engines! It's using the TaRDiS, and I can't stop it!"

"Never mind Cardiff, it's gonna rip apart the whole planet!" roared the Doctor.
Rose, a young blonde companion of the Doctor's, barreled into the TaRDiS. "What is it? What's happening?"

"Just little me!" cackled the plump, middle aged Margaret, an unearthly aspect to her wicked grin. She threw off one of her disguise's arms, and grabbed the younger woman with a hideous, green claw. "One wrong move and she snaps like a promise!"

"I might have known," muttered the Doctor, a tranquil fury setting in.

"I've had you bleating all night, poor baby, now shut it. You, fly boy, put the extrapolator at my feet!" Margaret tightened her grip on Rose's neck. Grimly, the Doctor motioned for Harkness to proceed.

"Thank you, sweetie," smiled Margaret, looking for all the world like a kindly grandmother with a green claw for an arm.

"I thought you needed to blow up the nuclear power station!" gasped Rose, trying to loosen Margaret's grip on her neck.

Margaret tutted kindly. "Failing that, if I were to be arrested, then anyone capable of tracking me down would have considerable technology of their own. Therefore, they would be captivated by the extrapolator. Especially a magpie mind like yours, Doctor. So the extrapolator was programmed to go to plan B. To lock onto the nearest alien power source and open the dimensional rift. And what a power source it found! I'm back on schedule, thanks to you!"

"The rift's going to convulse. You'll destroy the whole planet!" pleaded the Doctor.

"And you with it! Meanwhile, I'll ride this board over the crest of the inferno, all the way to freedom. Stand back, boys. Surf's up!" laughed Margaret, as she stepped onto the triangular extrapolator, riding it like a surfboard.

A huge groaning, wheezing sound and shrieking metal filled the air.

"Of course, opening the rift means you'll pull this ship apart."

"So sue me," sneered Margaret.

"It's not just any old power source." The Doctor stepped forward, perfectly calm despite the impending doom. "It's the TaRDiS. My TaRDiS. The best ship in the universe."

"It'll make wonderful scrap," sighed Margaret. "Is there a point to…?"

She trailed off as a wholly new sound broke the cacophony of sparks and thunder. It was a groaning, a rhythmic scraping that seemed to drown out every other sound. A panel on the main console of the TaRDiS popped open, throwing out brilliant golden light.

Rose's eyes widened, her eyes mirroring the gold. "What's that light?"

"The heart of the TaRDiS," said the Doctor, a bittersweet smile on his face. "This ship's alive. And you've opened its soul." He directed those last words at Margaret, who stood transfixed, all thoughts of escape banished from her mind.

"It's so bright…" she gasped.

"Look at it, Margaret." The Doctor quietly motioned for Rose to remain calm.

"…Beautiful..." Margaret murmured.

With the air of one delivering a eulogy, the Doctor addressed her by her alien name. "Look inside, Blon Fel Fotch. Look at the light."

Margaret dropped Rose to the ground, stepping forward into the brilliant gold light. She turned to the Doctor, a look of relief on her face.

"Thank you." She said, and disappeared into the light wholly.

The Doctor leapt forward, pulling down the console. "Don't look!" he shouted at Rose and Captain Jack. "Stay there. Close your eyes! Now, Jack, grab that extrapolator, shut it all down. Shut down! Take it outside! Rose, that panel over there, turn all the switches to the right! Except that one!" Captain Jack
dragged the extrapolator through the doors. Gradually the sparks and lightning died out.

Outside the TaRDiS, the lightning faded away and the sky returned to normal. Captain Jack turned and looked around. He sighed in satisfaction.

Inside the TaRDiS, the Doctor surveyed the damage. "Plenty of scorching, but that's normal."

"What about the light? Where did Margaret go? Did she just… burn up?"

"No, she's not dead."

"Then where did she go?"

"She looked into the heart of the TaRDiS, and even I don't know how strong that is. And the ship's telepathic, like I told you, Rose. Gets inside your head, translates alien languages. Maybe the raw energy can translate all sorts of thoughts." He looked at the floor near the base of the TaRDiS console. "Here!"

He held up a small, mottled green egg.

"That's her?" blinked Rose.

"Must have regressed her back to an egg. She's got a second chance at life, that's what she really wanted. But it's odd…"

"What?" asked Rose nervously. "I've seen that look before. That's not a good look."

"Well, it would take quite a bit of energy to regress someone like that…"

"Is that bad?"

The Doctor rubbed his head and pulled a face. "It shouldn't be…unless the Rift…if it was mostly open…at that exact moment…" His eyes widened and he sprinted to another control panel. "No, no, no!" The large tube in the center of the TaRDiS began pushing up and down, a groaning sound echoing all around them. The TaRDiS began to buck and shake.

Outside, Captain Harkness whirled around and stared at the Blue Box, whose light was now flashing in time with the groaning sound as the TaRDiS dematerialized.

"No! Not without me, Doctor! Wait!"

Inside, the doctor was desperately trying to wait. He flipped switches, pulled on levers and smacked at buttons. "We're being pulled through the Rift!"

Rose lost her balance and grabbed at the Doctor's shoulder. "Where are we going?!"

"I don't know, that's the problem!" Grab that lever, hold it down! Push that button twice!"

The TaRDiS spun into the Time Vortex, but instead of a red or purple-blue, the vortex was a searing white and orange.

And the TaRDiS spun right out of the universe, leaving Jack Harkness standing alone on a cool summer night, staring at where a blue box sat moments earlier.