AN: Thanks again to Bonnie for beta reading!

"' off," the Doctor tapped the screen a few times and frowned.

Cassandra nudged him away from the terminal and began to scan it herself, shaking her head. "When I was alone, those Nurse/Cat/Nuns were talking about Intensive Care. Where is it...?"

He glanced at her then quickly turned back to the screen. "Well done."

"Why would they hide a whole department?" She pulled back a bit as the Doctor reached into his jacket and pulled out the sonic screwdriver. "It's gotta be there somewhere. Search the subframe."

She didn't notice how his body tightened, nor how his eyes darkened. She would have noticed his clenched jaw, had he not forced himself to relax. "And if it's locked?" He watched her carefully as she rolled her eyes.

"Try the installation protocol," Cassandra enunciated the words as if speaking to a child.

He tensed again, and began running the sonic screwdriver against the terminal. The faint buzzing ceased after a few moments, and he stepped back with a tight smile as a portion of the wall slid away. "Well. Intensive enough for you?" He gestured toward the dark corridor blemishing the otherwise stark white walls of the hospital.

She smirked. "I suppose it will have to do."

He stopped suddenly and took her shoulders, staring deeply in her eyes. "Whatever is going on here, Rose, I will sort it. Understand?"

Cassandra blinked and nodded hesitantly, attempting nonchalance. "Well, of course you will."

"Come on," apparently she had not given him the answer he wanted. He led the way, not reaching for or even acknowledging her presence any further.

That the cavern inside had ever been hidden was hard to believe; it was massive in every direction. The metal stairs creaked under their feet, but they paid it no mind – indeed, could not pay attention to anything but the thousands of glowing green cells that lined every visible wall.

The Doctor held his screwdriver against a lock and pulled the door open. A man, propped up slightly, wavered in the enclosure.

"That's disgusting," Cassandra hissed. "What's wrong with him?"

"I'm sorry," he murmured, expression soft for the first time since Cassandra had joined him. She backed away, covering her nose and mouth with her hand. The Doctor closed the door gently and moved to the next, only sagging more when he saw a woman inside in the same condition as her neighbour.

"What disease is that?" Cassandra asked, disgust still lacing her voice.

"Everything. Every disease left in the galaxy, they're forcibly infected." He closed the door and looked over the cavern. "Lab rats, tortured from birth like animals. That's why they have cures when no one else does – no one else would do something so disgusting."

"Why haven't they died?"

"They're carriers. Always the last to die."

A new voice, gentle and sad, pulled their attention to the end of the row. "It's for the greater cause," Novice Hame informed them softly.

"You agreed to this? This was part of your vows?" The Doctor's voice was rising steadily.

"The Sisterhood has sworn to help," she replied, lowering her eyes.

"Help who exactly? Not these people – not the living beings tortured beyond recognition!"

"They aren't real people," she corrected him gently. "They are grown here, for this purpose."

"And how many have died? How many a day – a year? For how many years? How many, Novice Hame, answer that!"

"Mankind needed us. They came to this planet with so many illnesses. We couldn't cope. We did try. We tried everything. We tried using clone-meat and bio-cattle... but the results were too slow. So the sisterhood grew its own flesh. That's all they are. Flesh. "

"They're alive, Hame."

"And so are thousands of people, living real lives, out there in the city...people who would have died if not for us."

"Ah," Cassandra interrupted, ignoring the ever-increasing tension in the Doctor's shoulders. "Just to confirm, none of the humans actually know about this?"

Novice Hame hesitated, her expression dimming. "Well, we thought it best not -"

"Stop," the Doctor clenched his fists and took several deep breaths. "Let's ignore that, for now." Novice Hame took a step back as his voice became deadly quiet – far more terrifying than any shouting could ever be. "All of this, I get it – the road to hell and all. But what have you done to Rose?"

Hame glanced at the blonde and shook her head slowly. "I don't know what you mean."

"You need to be aware of somethin'," his tone didn't change, but Novice Hame was suddenly struggling against an instinctive desire to flee - although she would never admit it, the top of a very tall tree seemed the best destination. "And that's the fact that I am being very, very calm right now. Were I not very, very calm I might tear this place down bare-handed – and I'm not going to risk her mind. So you will reverse whatever you've done and you will do it now."

"We haven't done anything," Hame tried to say again, still backing away, very slowly.

"I'm perfectly fine," Cassandra attempted.

The Doctor ignored her, the full focus of his intense blue gaze still resting on Novice Hame. "Rose does not know about installation protocols and she definitely cares when people are being killed. So I'll ask one more time -"

"Oh, all right, clever clogs," Cassandra snapped, pulling the Doctor to face her. She ran her hands along his lapels, her nails scratching the leather gently. "Smarty pants...lady-killer."

He grabbed her wrists and pulled them away from his chest. "What's wrong with you?"

"I knew something was going on in this hospital, but I needed this body and your mind to find it out."

The Doctor's grip on her wrists tightened and he glared into familiar eyes and felt an unfamiliar mind staring back. "Who are you?"

She leaned forward, pressing her palms against his chest again. Her breath tickled his cheek as she shared her identity. "The last human," she whispered softly, for his ears alone. She smirked for half a moment before leaning a bit further and biting his earlobe playfully.

He shoved her away roughly, eyes dark and furious. "Cassandra," there was surprise in his tone, hidden deep beneath his anger and disgust, to which she smiled. "What did you do to her?"

She held up her wrist so he could he saw the small black device there – and he fairly vibrated with fury. "It was surprisingly easy to lure her away, just a few whimpers from my sweet pet Chip and she was holding his hand and trying to comfort him. I knew someday I would find someone worthy of sharing in my beautiful essence, I had it all prepared."

"That thing is banned on every planet for a thousand light-years," the Doctor grabbed her, pressing his screwdriver to the pyschograft link at her wrist. "Let her go," he growled.

"I think not," Cassandra smiled. "And any attempt to force the issue will cause an unfortunate overload of her cerebral cortex, leaving it a bit...liquid. You try to push me out, I take her with me."

He levelled her with his darkest stare. "I will get you out of her, Cassandra."

"Oh, you can have her back as soon as I find someone younger and...less common," she shrugged and tugged herself loose – noting with a good deal of concern the way his hands flexed into fists as she slid from his grip.

"Right," he spun back to face Novice Hame, who'd observed the exchange with equal parts confusion and horror. "Where're the controls for this system?"

She pointed a trembling hand to a panel on the wall. "But – what are you doing?"

"You got the cures to every disease in the world?" He put the sonic screwdriver in his teeth as he pried open the cover. "I'm going to administer them."

"Oh, no," her voice broke. "No, you can't – we haven't enough! The patients upstairs, the real people -"

"These people deserve to live!" A familiar blue light filled his hands as he pressed the tool against the computer system. "All they need is a drop each – their immune systems are primed to heal. They just want a bit of a boost."

"I am afraid I cannot let you do that," Matron Casp stood at the end of the hall, eyes flashing gold in the dim light. "The flesh must remain as they are."

"You lot'll get what's comin' to you in your own time!" The Doctor snapped, not lifting his eyes from the computer terminal.

"And who will arrange that? You?" The Matron smirked. "You underestimate us, Doctor."

"Yes. Me," he turned his head to meet her stare, unblinking and silent.

Sister Jatt shifted awkwardly beside the Matron, lowering her eyes. "We heal those above, Doctor, isn't that good enough?"

"No." He turned back to the screen, and the sonic screwdriver flashed a few more times before it was turned off and sparks began to flash from the controls. He straightened, shoving the tool in his pocket once again. "You try touchin' that, even the slightest attempt at overridin' my orders and it's primed to fry every control in this place – includin' the ones keepin' them in. Don't touch it."

"Oh," Matron's voice was steady. "I think you might regret that. We have no intention of allowing this destructive behaviour to continue."

"And how do you intend to stop me?" He folded his arms and leaned against one of the glowing doors. "Goin' to point a weapon at me? How's that rank in your vows?"

"Our vows demand only that we work for the greater good," Casp replied, her lips curling sinisterly. "Fortunately, the order has never been terribly particular about methods..." she raised her hands and he became very, very aware of the sharp, thick claws at the ends of her fingers. "Jatt! Call up the Sisters!"

The Doctor spun and grabbed Cassandra's hand, pulling her with him. "Run!"

They ran.

"What are we going to do?" Cassandra was breathing heavily; the body was used to running but the mind wasn't used to the strain of it.

"You're going to leave that body," the Doctor replied, not even looking up as he secured the door with his screwdriver. "You're going to die, and Rose is going to live." He turned around and let the full force of his glare hit her.

"Fascinating, really, but wrong. As long as I'm in this body," she ran her hands over the curves in appreciation and saw his jaw tic slightly. "You will do everything you can to protect me. And I'm beginning to get comfortable."

"No," he corrected, striding forward. "That's not how it works. You're compressing Rose, you'll kill her either way if you stay. And if you do that, there's nothin' in this universe that will be able to keep you alive, Cassandra."

"And if I leave I die anyway," she pointed out. "My original skin is dead!"

"That's your own fault!" He aimed his screwdriver at a contraption on the wall and then to the link on her wrist. "You didn't get her in the psychograft itself, you haven't got the control you should. You can already feel it – you're going to melt in there."

She pressed her fist to her mouth, biting back a sob. "I don't want to die."

"Everything dies."

"I could take her with me," Cassandra looked at him through watery eyes. "You deserve it, both of you."

"Cassandra," his voice was velvety smooth, but the steel was beginning to show. "Give her back to me."

"You want her back so badly? Fine. You asked for it," a pale pink mist seemed to flash from Rose's body, careening across the room toward the Doctor's body...and dissipating, mid-air.

Rose swayed and felt her knees buckle, but strong, leather-encased arms wrapped around her before she could fall. She tried to get her legs under her, but only managed to stumble deeper into his embrace. "Oi, now!"

She glanced up and saw blue eyes and familiar smile. "Hello," she murmured, smiling back.

"Hello!" He helped her stand but didn't quite release her, his eyes moving quickly over her and his hands maintaining contact at her waist. "Alright?"

"Yeah," she patted his lapel, as if attempting to smooth it. She smiled at him again. "Hello!"

He grinned and moved a hand to cup her cheek. "Welcome back."

She giggled nervously. "Our holidays are never boring."

"Nope, excitin', that's me," the pad of his thumb caressed her cheek lightly. "Luckily, I'm brilliant and solved it all."

"What d'you mean? Where'd Cassandra go?" She pulled back and looked up at him curiously.

He grinned and twirled the sonic screwdriver. "Well, a typical application of a psychograft lets the consciousness jump from host to host, uses the brain like a sort of transmitter. But to get to you, Rose Tyler, she had to use a booster signal," he twisted Rose's arm to show her the link. "And she didn't pay near enough attention to the settings on my screwdriver. When she tried to jump, I reversed the signal."

"So...where is she?" Rose glanced around the room – the ruined brain matrix bubbling useless in one corner.

He tapped a button on the psychograft link and it dropped from Rose's arm; she immediately pulled it close to her chest as blood beaded where the wires had been. He held it up, smirking. "Rose, meet Lady Cassandra O'Brien.Δ17."

"She's in there?"

"Yup," he grinned wider.

"You think you're so clever," she couldn't help smiling back.

If he'd had something to say in response, he didn't get the chance. The atmosphere was shattered as the Doctor's careful securing of the doors failed, and nurses appeared in the entryway – hissing and spitting as they ran into the room.

"Up!" He threw one of the IV stands at the leader, tripping her as he and Rose raced for the ladder. "Quick, Rose, move!"

"I'm goin'!" She pulled herself as quickly as she could, the Doctor right behind her – and a dozen catkind nurses just behind him.

The climb itself would have been exhausting enough, but with the speed Rose soon felt her arms tiring.

"Just keep goin'," the familiar bass drifted up from the Doctor. "I can open that elevator shaft once we get there, don't slow down!"

"I'm not!" She pushed herself harder, moving faster.

He let out a grunt and she looked down to see one of his heavy booted feet caught in the claws of Matron Casp. He jerked, but the feline grip only tightened. "Oi!"

"Doctor!" Rose hesitated, looking desperately for something to throw at the nurse.

"Keep going, Rose!" The Doctor struggled, wrapping his arms around the pole and managing to place a solid kick. There was a sickening crack, and the Matron's head twisted at an odd angle. Her grip loosened and gravity took hold of her...along with several of the nurses climbing below her. When he looked back at Rose his eyes were dark, but he was climbing again and so she did the same.

It seemed like an eternity before they reached the top, but the catkind were still close behind.

The Doctor stopped below her and pulled out the sonic screwdriver, scowling as he flipped through settings. "No good, I can't reach. Can you climb higher?" He looked up hopefully, but she shook her head as she held tight to the top rung. "Right, don't mind me then," he held the instrument between his teeth and continued to climb.

Rose held herself very still as the Doctor leaned against her and grabbed hold of the the screwdriver again, this time opening the door. He jumped through gracefully then pulled Rose inside. He slammed the door behind and sealed it, then turned to her with a grin. "That was fun."

"Thrill a minute," she laughed a little. "So how do we get out?"

"Easy," he grinned. He pointed to a computer terminal. "I'd say that cure is just about worked by now, wouldn't you? What d'you say we let out our little friends?"

'All staff will present themselves to the officers for immediate arrest. I repeat -- immediate arrest. All new life forms will be catalogued and taken into care. All visitors to the hospital will be required to make a statement to the NNYPD.'

The Doctor watched with satisfaction as the nurses were being led from the hospital. Novice Hame caught his eye, and his smile dropped. There was a short pause, then he grabbed Rose's hand.

"The Face of Boe!" He jumped into action, dashing for the far side of the ward.

He grinned as they approached the fully conscious Boekind. The Face smiled back, showing only the faintest hint of weakness.

"Thought you were dyin'," the Doctor stated casually, leaning against one of the struts.

There are better things to do today. Dying can wait.

Rose jerked and went wide-eyed at the sensation.

"Telepathy," the Doctor squeezed her hand gently. "Now, hush."

"I didn't say anything," Rose hissed at him.

I have grown tired with the universe, Doctor, but you have taught me to look at it anew.

The Doctor moved forward, tugging Rose with him. They knelt in front of the glass, and he pressed his free hand against it. "Legend says you're millions of years old," he said instead.

Well, now that would be impossible.

The Doctor grinned slightly. "Guess so. An' you wanted to see me?"

These legends...they also say that I have a great reveal to a lonely traveller.

"They do that," he agreed, squeezing Rose's fingers.

It can wait.

"It can?" His face fell. "Bit ungrateful, after the trouble I've had today."

We shall meet again, Doctor, for the third time... for the last time... and the truth shall be told. Until that day... with a soft buzz cool blue glow, he teleported away.

The Doctor stood, frowning at the spot. "Enigmatic, that's what he is. Oh, well done." There was a long pause and he glanced down at the blonde by his side. "No more wanderin' off for you," he informed her a bit severely.

"What, me? You're the one who -" she was interrupted a bit roughly by a face full of leather – specifically, his jacket. "Oh."

He hugged her tightly for just a moment, then released her with sudden cheer. "Enough chit-chattin', no point in hangin' around this sad place. There's a whole city over there and you haven't seen a bit of it. I believe you ordered New Broadway?"

Rose hugged his arm as they walked; her lips curled up in a bright smile and she rested her head lightly against his shoulder. "Fantastic," she replied.

He grinned.