This is about the Doctor and Jack Harkness.
So, okay, the whole thing where Jack blames the Doctor for leaving him behind on Platform One.... I can see how it would seem like that to Jack. And I can even understand what the Doctor says about Jack being a fixed point in time and space (and if Jack wasn't an established character whom I like, I'd be yelling "Marty Stu" after that statement), and thus being really off-putting to a Time Lord.
That explains why he didn't open the door for him when he saw him at Cardiff (and even explains why Jack went so long NEVER finding any of the Doctor's incarnations--he'd be avoided just by instinct).
Doesn't explain why the Doctor seems to take the blame for leaving Jack in the first place. How'd he even know Jack was alive? Does this come up again? Because it's not making sense to me, and it really makes the Doctor look like a jackass.