It's the bloke's guitar that first causes her curiosity, with the worn case covered in stickers that Donna Noble just can't ignore. A little glimmer of recognition, maybe. She's just not sure.
And maybe he notices her stare, because he grins excitedly and offers up meager conversation, same old boring chit-chat that strangers make when they've got nothing better to do.
Charlie Pace. Former bassist for Drive Shaft.
Donna Noble. Best temp in Chisick.
(She laughs when their introductions get the exact same wide eyed stares.)
It continues normally, their conversation, with Charlie discussing his failed music career and she lamenting about her failed engagement (not too much, leaves out the stuff with Space Boy and his Magic Box), hopes and dreams and their plans for the next five years or whatever they discuss.
They get off at the same stop, walk the same route, and when he stops just short of her office building she presses a wad of bills and her number into his hand.
"Hope this helps, Rocker Boy."
Charlie thanks her, Donna leaves. This could be the start of her moving on.
(Charlie calls a few weeks later. Donna's spaceman has come back, she's already gone.)