Xander's watching Spike at Giles', back when he was in the bathtub, and he loses track of time. He forgets to feed Spike and when he does go to bring up the blood, he hears Spike talking to himself saying things like, "They didn't forget you, Will. They wouldn't let you starve. No, don't cry. Don't do this to yourself." And then Spike cries and Xander feels pretty dang bad for everything. And Xander goes back down and makes noise coming up so Spike knows he's coming.
I think it's probably part of a much longer fic (that eventually leads into Spander!land) but I don't remember anything else that happens... It's near the beginning of the piece, I know that much. Heck, I might even have the page saved but I can't remember enough to find it (I've got quite a few of my favourites marked). Any assistance would be appreciated.