Maia Roberts hates Jace because he reminds her of her terrible older brother, Daniel, and her ex-boyfriend, Jordan.
Actually, the only thing the two have in common is that they're all "beautiful boys" (1.2.1). Both Daniel and Jordan were crazy and abusive. Jordan even bit her once, and she turned into a werewolf. Whoops. She's hung out with the downtown wolf pack ever since, the one with Luke as pack leader.
Jace has come into the wolf bar, The Hunter's Moon, and is acting like himself, i.e. a cocky jerkface.
Jace ends up starting a fight with a wolf named Bat, but the kerfuffle is interrupted when someone bursts into the bar saying there's been an attack outside. A kid is dead.
The witness says the kid was killed by a something that wasn't human. The werewolves assume that a vampire did it, which is ironic considering they have a wolf named Bat in their ranks.
They turn to Jace saying, "the Clave owes us protection in these circumstances" (1.2.50).
Jace gives them attitude ("It's a little too late for him to need protection" (1.2.53)) and another skirmish ensues.
Luke breaks this one up and takes Jace to the office to talk. He calls Clary and tells her to come down to the Hunter's Moon.
Simon is annoyed that Clary is rushing to Jace's side, but she asks Simon to go with her.
When Clary arrives, Jace continues being as unpleasant as possible, but he tells them that the Lightwoods kicked him out.
He says he'll get a job in the mundane world and live there, but Clary reminds him that he has no marketable skills other than killing demons.
Luke recommends that Jace return to the Institute and try to talk to Maryse, instead of just storming out like he just did. Clary agrees to go with him.
Outside the office, Maia approaches Simon to flirt with him a bit, and to tell him that Magnus Bane has arrived and wants to see Luke.