And Sarah Jane Smith shakes her head. "No...I can't do this anymore." Their smiles fade, but hers grows brighter and brighter: "Besides, I've got a much bigger adventure ahead! Time I stopped waiting for you and found a life of my own!" Mickey -- remember him? -- clears his throat. "...Can I come?" Sarah Jane looks surprised, but Rose knows what he means. And finds it yucky. "No, not with you, I mean...With you," he says -- and this is essential -- pointing at the Doctor. "Because I'm not the tin dog. And I wanna see what's out there." Rose's lovely mouth forms a perfect NO, but there's no stopping this. Mickey finally wants in for the right reasons, and he isn't unafraid. His adventures have made him a worthy Companion, and the Doctor only takes the best. "Oh go on, Doctor," says Sarah Jane. "Sarah Jane Smith -- a Mickey Smith. You need a Smith on board!" The Doctor makes a show of deciding, then: "Okay then, I could do with a laugh." Rose rolls her eyes. This Companion gig gets less and less special all the time. Maybe one day soon you won't be able to tell the difference anymore. Mickey laughs, delightedly, but stops at her face: "Rose, is that okay?" She pulls a horrible face, not that I blame her: "No, great. Why not?" Awkward. Sarah Jane's like, "Yikes. Gotta bounce."
Sarah Jane Smith takes Rose aside; the Doctor turns back to the computer like he's invisible. "What do I do?" asks Rose, glancing at the Doctor. "Do I stay with him?" That's not what she's asking: she's asking about what happens next, and about what doesn't happen next, and what happens after that. It's the latter set of questions Sarah Jane answers: "Yes. Some things are worth getting your heart broken for." She embraces her young double, this lovely young ex-rival she's learned to love: "Find me...if you need to, one day. Find me." Rose gives her a small smile. (Never. Might as well join LINDA, about whom we'll be hearing a goddamn earful down the road. No matter how many secrets they both know, they're still personal. What's sadder than one ex-Companion? Two of them. What's sadder than that? Becoming an ex-Companion before you're thirty, and hanging out with an old journalist and her secret talking dog. I'd die first. Find myself on the other side of Hell from that. Or, I don't know, like, Norway or something. Don't even give me your number, Sarah Jane!)
The Doctor holds open the doors for Sarah Jane, who steps out from the TARDIS for the last time. They stand in the sun, for their last goodbye. It's too bright. (And in the air you can hear a slower, sadder "Song For Ten." And if it wasn't instrumental, you could hear a man singing: "'Cause I followed my star/ And that's what you are/ I've had a merry time with you/ I wish today was just like every other day...") "It's daft," says Sarah Jane, with a smile, "but I haven't ever thanked you for that time, and like I said -- I wouldn't have missed it for the world." The Doctor smiles at her and makes assumptions: "Something to tell the grandkids." "Oh," she smiles, "I think it'll be someone else's grandkids now." That throws him off. "Right. Yes, sorry -- I didn't get a chance to ask. You haven't...there hasn't been anyone...? You know...?" (To her, perpetual maidenhood, And unto me no second friend.) "Well," she smiles sweetly. "There was this one guy. I traveled with him for a while. But he was a tough act to follow." The Doctor smiles back at her with all the love in the world; they wish today was like their days before. "Goodbye, Doctor," says Sarah Jane, and he jumps in with his clarion call: "Oh, it's not goodbye..." She tries to explain Season 2 to him (again): "Say it, please. This time. Say it." And he looks into her eyes, respectfully, sad and shining, and he says this: "Goodbye. My Sarah Jane."