The very atmosphere in the TARDIS was taut with uncertainty.
The Doctor clenched his teeth together as he writhed on the rough metal grating, requiring the quick intervention of both Rose and Donna. Their hands desperately braced his shoulders so as to keep him from injuring himself further. But even if he were to cause further damage by thrashing around, it would do little to increase the futility of the situation. Try as he will, as he watched the scene play out in front of him like a nightmarish cutscene, powerless to enact any control over the scenario, Jack couldn't ignore the inescapable truth. Genuine fear brimmed within that man's pained expression. Despite his alien physiology, the humanity he carried within him was bubbling to the surface.
That Doctor, that beautiful man... he didn't want to die.
"What's going on?" Donna said, actively resisting Jack's pull as he tried leading her away from their friend, lying prone on the floor.
"I told you, he's dying."
"Well, we can't just stand here!" she cried, eyes damp and reddened, and god did the sight of her hysteria make him wish there was something he could do to fix all of this, some magical cure-all stored back at the Hub he could pull out of his ass to reverse all of this, to turn back the flow of time. "We need to do something! We need to help him!"
She shoved past him, her path set solely for the Doctor, but Jack caught her by the wrist. The sheer look of betrayal she hurled at him as she struggled in his grasp stung like a dagger through his chest, but he held tight. It wouldn't be safe. While he desperately wanted to help— the Doctor's stertorous breaths were becoming increasingly painful to listen to— he saw a faint glow lingering in his veins. He'd read up on the old tales of the Time Lords over the years, educated himself as much as he could, and he knew how destructive this process had the potential to be.
"No, we need to stay back! Rose, you too! Get back!"
Rose Tyler crouched by his side, blatantly ignoring his warnings in the throes of her grief. "No, please, don't die—!" Her hand quivered as she tried to mop the sweat off her Doctor's brow. "Not now, not when I just found you!" His gaze locked with hers, packed with more unspoken sentiment than Jack ever imagined could be transmitted through mere expression. She let out a keening cry at this, evidently gaining more from this single glance than anyone else ever could, and immediately pressed her hand to her mouth to keep from losing her composure entirely.
"I- Rose," he rasped. "I- I'm sorry, I'm sorry, I can't stop it. I'm..." He paused, sudden panic flooding across his face. "Jack," he said frantically.
He didn't— couldn't?— complete that sentence, but Jack understood. Get Rose to a safe distance. Heart aching at the thought of separating them but knowing it was for her own good, he vaulted across the console room to her. Though she still reached out for the Doctor in silenced desperation, she was already standing up. Oh yes. He almost forgot in all the confusion; she was the one person in this ship who'd seen this before.
Here we go," he said, leading her away from the regenerating Time Lord. "Good luck, Doctor."
"Will someone please tell me what is going on?" Donna begged, as the Doctor spent every last parcel of time left to pull himself to his feet.
"When he's dying, his... er, his body, it repairs itself," Rose explained. "It changes. But you can't!"
The Doctor clutched to the side of his ship's console like a lifeline, his striated breath painful to hear. "I'm sorry, it's too late. I'm regenerating!"
Then he stepped away from the console, threw back his head and arms, and was consumed by violent fire. Instinctively, Jack and the two women turned away. His arms tightened around their shoulders, fingers nearly digging into their skin. He somewhat wished he could cover his ears to dampen the whistling roar of regeneration, but he couldn't, at least not holding Rose and Donna. Was it at all taboo to watch a regeneration, he wondered? To the Time Lords? He couldn't deny he was curious, but for the first few moments he held back, as if worried the ghosts of Time Lords long passed would manifest to curse him into an eternity more hellish than the one he already intimately knew. Curiosity finally got the better of him, however, and Jack squinted so he could watch. After all, this process was something that had dissolved into legend. Few had ever witnessed this.
He could see his friend's face, almost completely obscured under rippling waves of golden energy. His mouth was contorted into a grimace, and his eyes were screwed shut. Then, startling him with sudden movement, the Doctor forced his outstretched hands together and aimed the regenerative energy at the glass receptacle containing his severed hand. The energy flowing from his hands and head began to grow thin— as if it were seconds from running out— but at the last moment he let out a sharp shout, his body wrenched upright by unconscious force.
Jack watched the moment his features morphed into another's, and to his surprise it happened as quick as a snap of the fingers.
The new man stumbled over his feet in the chaos of it all, almost colliding into the pillar. He was wide-eyed and youthful, with somewhat shaggy brown hair that almost fell like a curtain in front of his eyes. He looked down at his body in shock.
"Doctor—?" Rose hesitantly edged towards him. But if he noticed her presence, he made no visible sign of it.
"Legs!" he proclaimed joyously instead, his unused voice cracking. "I've still got legs! Good!" As he gazed at his feet, still gasping for breath, his thin brows furrowed in thought. "Could've been worse, I suppose," he muttered.
Donna, mouth agape, lifted a solitary, accusing finger towards him. "Oh... my god! Just when I thought I knew everything about you, you go and change your face!"
"It's called regeneration," Jack offered weakly, genuinely feeling mentally drained from all he'd just witnessed.
Without a moment of warning the Doctor hit himself on the forehead with his palm, startling his friends. "Oh, Rose! Jack, Donna! Blimey, no, no, no, no, no! This is all a-" he massaged his temples wearily- "...a huge mistake. This wasn't supposed to happen! But, there's something else, something important..."
They all stared at him blankly, waiting for him to finish.
"Am I ginger?"