Fis Search

I'm looking for a fic that I read awhile ago. Willow is practicing magic by making a potion while she's alone at the Box. When Giles comes back, she hides it in a cup because she's not supposed to be doing magic unsupervised, I think. Giles washes some cups and Willow thinks he dumped ot her potion, but at the meeting that night Xander drinks the potions, thinking it'sjuice. He ends up turning into the kind of demon the potion was supposed to banish. (After this point I may be mixing fics.) I think the kind of demon he is can move through solid objects. Um, Willow summons a demon, takes its power and goes on a demon killing spree which includes killing everything in the Alibi Bar including Willie. I think Buffy is dating an Angel look alike. The LA gang ends up coming to Sunnydale to help. And the demon of the week (the one Willow summoned?) makes people vulgar and crazy while uses their senses to watch the gang. I think.
Anyone recognise this?