Episode 59 of "Buffy, the Vampire Slayer"
s04e03 The Harsh Light of Day
Title: The Harsh Light of Day
Original Air Date: 10/19/1999 on WB
Director: James A. Contner
Writer: Jane Espenson
Plot Outline:
Spike returns to Sunnydale with his new girlfriend Harmony who is now also a vampire. Spike is searching for the Gem of Amara - a stone which makes vampires invulnerable, which he believes is buried somewhere under Sunnydale. Buffy is preoccupied with her budding relationship with Parker and sleeps with him but he proceeds to ignore her. Meanwhile Anya returns and throws herself at a flabbergasted Xander.