He asks her to go with him. Her first instinct is to say no. He's completely mad and a bit suicidal, and his cold detachment is just so alien.
The word catches in her throat.
Donna remembers the Doctor's laughter, like delight bursting through the cracks of his shattering pain from losing his friend. She tells herself that she's hesitating because she doesn't want him to be on his own. That's not it, though. Not really. He's got all of time and space to offer; he could find someone else to keep him company in minutes.
She's also just not that selfless.
The real issue is that she's never felt this alive until today. Nothing could ever measure up to that life that she's barely glimpsed. It's not even about being able to travel back to the creation of the Earth or whatever. It's more that... she helped save the world today. Her, Donna Noble, just a temp from Chiswick. Probably no one will ever know (they'll certainly never believe it), but she'll always remember. With that knowledge comes a hope that she's worth more than a string of dead-end jobs and the search for a husband. It's a bright, shining memory in an otherwise fairly monochromatic life, and she can't help but want so much more of that.
She finds herself nodding. "Yeah, all right," she says. "As long as you don't think you're gonna whisk me across the universe and never bring me back, alien boy."
She says it like it's a joke, but behind the facade of her smile is actually the most serious question she's ever asked a man (including "Will you marry me?"). He could get her killed, or he might just travel around where and how he likes with no regard for whether she wants to come back to Earth. Either way, she knows she's taking the chance that she'll never see her family or friends ever again.
She doesn't want to contemplate that too closely. If she does, she won't take the chance, and she really feels that she needs to.
"The TARDIS isn't a prison ship," he says roughly, a hint of hurt shadowing his expression at the implication. "I'd never keep anyone with me against their will. You're not promising me forever just by stepping inside."
Donna's clearly hit a nerve without meaning to (she does that a lot). She wonders if his friend left him because she'd wanted to go home, though Donna can't help but think that in that case he might have gone with her. Even with all of time and space at his whim, it doesn't seem worth the way his eyes look deadened.
She wonders whether she'll ever know the truth about what happened with that woman. If he won't tell her about something that's clearly so important to him, how can they travel the universe together?
Still, Donna's always been brilliant at wearing people down.
"Just tell me something. That friend of yours," she says. "What was her name?"
He hesitates, but he does eventually share with her after all.
"Her name was Rose."
She hears the emotion in his voice. It makes it clear that he isn't shut off because he doesn't care. He just cares too deeply.
For now, she thinks that's enough to be getting on with.
He actually waits for her while she runs inside to tell her family she's leaving. She thinks that might be something to hold onto too.
He fixes her phone so she can ring home across time and space. She imagines hilarious secretive phone calls to her Grandad, sharing the details of alien landscapes that only he would believe she's actually seen. Instead, the first call she receives is from her mother.
She turns stunned eyes to the Doctor. "My Dad..." she breathes.
He takes the phone gently from her hand and asks her mother what the current date is for her. Donna thinks that, even above the dull ringing in her own ears, she can hear the incensed tone of her Mum's voice in response to what must seem like a truly ridiculous question.
The Doctor sets course for Earth without Donna even having to ask.
Donna realises that she was foolish to think he wouldn't take her home the second she needed to go. He's lost his whole planet and species. He's lost Rose. Of course he understands the value of family.
Clearly she's become something like family to him; he hugs her just the way she needs when she finally bursts into wracking sobs.
They've barely been back travelling again for two weeks when the Doctor nearly gets himself killed (again) saving the lives of an encampment of slaves on some planet with a name beginning with 'C', which Donna can't quite pronounce. She's not surprised that he'd do that. Even though it's annoying, and he'll get a right smack for it later, she also sort of expects it when he makes sure that she's well out of the way before he goes about trying to martyr himself.
These things do bring about a realisation of sorts, though.
She trusts that he'll save the universe; he never gives up and he's willing to do what's necessary. She trusts him with her own life; she knows that he'll do absolutely everything he can to protect her. She knows that the life they lead is still dangerous, but she thinks that she's probably still safer facing homicidal aliens with 'the Oncoming Storm' watching her back than she is crossing the average street back home (especially the constant way London cabbies nearly run people down).
Whatever her first impressions were, Donna realises now that she really does have faith in him.
With his own life, though? Donna doesn't trust him with that for a moment.
It's just as well that she decided to travel with him after all, she thinks. Someone's got to keep him from doing anything especially idiotic.
~FIN~