After the events of the two-part episode "This Year's Girl" and "Who Are You", Faith (Eliza Dushku) leaves Sunnydale and goes to L.A. in the Angel two-part episode "Five by Five" and "Sanctuary" and is hired by Wolfram & Hart to kill Angel.
Angel visits Sunnydale again in "The Yoko Factor" to apologize to Buffy after the way he treated her in "Sanctuary".