Rose makes herself comfortable on the jump seat. The trip to New Gallifrey will take a few hours.
The Doctor, as usual, is dashing from one side of the console to the other, turning dials and flicking switches. Rose is content to just sit and watch him. She still finds it hard to believe that she is here, with him, forever.
Lost in her thoughts, she doesn't notice that the Doctor has ceased his activity until he is standing in front of her. He reaches out and tucks a wayward strand of hair behind her ear. She gives him one of her trademark grins, tongue just peeking out from between her teeth.
He joins her on the jump seat and pulls her into his arms. She snuggles into him, her head resting over his left heart. They stay like this for some time, content just being together.
The Doctor is about to ask Rose if she has gone to sleep when he hears her sigh. Looking down at her he notices a golden glow forming in her eyes. "Not again," he thinks to himself.
Rose/Bad Wolf pulls out of his arms and turns slightly so that she is facing him. When she speaks he notices that her voice is almost normal, only a hint of Bad Wolf about it. "It's me, Doctor. Rose," Rose tries to assure him.
"If that's you Rose then why are your eyes glowing?" the Doctor asks her.
"Bad Wolf and I are trying something out, to see if I can still hear and speak when she is awake. So far so good," Rose replies, winking at him cheekily.
"Right, well, fine then," the Doctor says, running his hands through his hair.
Rose grabs his lapels and pulls him close, giving him a long, passionate kiss. When she finally comes up for air the Doctor smiles at her ruefully. "Oh yes, you're definitely you!"
"Oi," she says, playfully swatting at his arm.
He holds his hands up in mock surrender.
Rose just shakes her head and laughs at him. "I was hoping to have a serious conversation with you, Doctor, before we get to New Gallifrey!"
At this the Doctor becomes serious, all playfulness forgotten. Rose notices his changed expression and rushes to allay his fears.
"It's nothing bad, Doctor." She takes a hold of his hands and gives a gentle squeeze. "I just wanted to ask you about regeneration. You still haven't explained it to me, not properly. I was wondering, why didn't you change after that Dalek shot you? You did on Satellite 5, after you absorbed the energy from the Time Vortex."
The Doctor pulls his hands free and jumps up. He starts pacing back and forth, running his hands through his hair. This is the last thing he expected to be having to explain.
"Well, Doctor?" Rose prompts him.
He stops pacing and turns to face her. Taking a deep breath, he launches into full lecture mode. "Let me start at the beginning. Time Lords have a process called regeneration which helps us basically cheat death. When we are mortally wounded or our bodies worn out from old age, we regenerate. All the cells in our bodies are replaced with new ones. Every single one. All that remains are our memories, and even they are sometimes scrambled. When I absorbed the energy from the Time Vortex all the cells in my body were damaged, dying. I didn't just remove the energy from you; I repaired the damage that it had done…."
"So you changed because of me?" Rose interrupts him. "I was trying to save you, but I killed you…," she trails off with a sob.
The Doctor moves over to her and pulls her into his arms, shushing her, rubbing her back. "Oh no, Rose, you saved me. If you hadn't come back the Daleks would have destroyed me. They would have shot me over and over until I had no regenerations left. You kept that from happening. You spared me from that nightmare."
He pulls back from her slightly and puts a finger under her chin, raising her face to his. He wipes her tears away and gives her a gentle kiss.
"Okay now?" he asks her tenderly.
"Yeah," she says, giving him a weak smile. She pulls away from him then and sits up a bit straighter. "Hey, what did you mean about the Daleks? How many regenerations do you have?"
"Time Lords are given 12 regeneration cycles…," he breaks off as Rose interrupts him.
"How many have you used then?" she asks anxiously.
"I've used 9 now, this is my tenth body."
"What about when that Dalek shot you. You started to regenerate then but you didn't change. Why not?" She looks into his eyes, as if seeking the answer there for herself.
"I healed myself using the regeneration energy but I didn't want to change so I redirected the energy into my spare hand." He breaks eye contact, almost as if he is embarrassed.
"Why didn't you want to change, Doctor?" she prompts gently.
He takes a deep breath and lets it out slowly, gathering his courage. "I wanted to stay the same for you. You'd only just found me again and I couldn't do that to you after all that time apart. When I regenerated after Satellite 5 all I was thinking about was you. I wanted to look good for you. I have no control over what I am going to look like when I regenerate but I thought if I kept you in my mind then maybe that would help. And it seemed to work. I didn't want to go through that again. Besides, I love this hair!"
"I love your hair as well!" Rose exclaims, running her fingers through said hair. She takes a few moments to absorb all that he has told her. "If you were able to heal yourself without changing after the Dalek shot you, why didn't you do the same thing after Satellite 5?"
"Once the regeneration process has started there's no stopping it. I only redirected the energy into my hand; I didn't stop the regeneration itself. If that hand hadn't been there then I would have changed. The energy can only be redirected into a matching biological receptor – a severed limb if you will."
"So you've really regenerated 10 times then," Rose states.
"Well, I'm not sure if that last one really counts. Time will tell!" he grins.
"And you're sure there's no way to control the regeneration energy?" Rose asks him.
"Absolutely positive," he replies. "Why?" he asks her, suddenly suspicious.
His suspicions are confirmed when he notices the golden gleam in her eyes. "You'd better rethink your answer, Time Lord, before we get to New Gallifrey!"
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