Buffy The Vampire Slayer (1997) - 4x08 - Pangs

Angel covertly comes to Sunnydale fearing Buffy is in danger after Doyle's vision of her in Angel.
While digging for a new Cultural Centre at the college, Xander falls into a sacred Indian burial area and releases Hus, a vengeance spirit of the Chumash Indians, the original residents of the Sunnydale area. Buffy is busily planning a traditional home cooked Thanksgiving while people around Sunnydale are being killed and Xander gets sicker and sicker. Hus summons a group of warriors and they attack Buffy and the gang at Giles' house. With Angel's help they repel the attackers until Buffy finds a way to kill Hus.
As they sit down to dinner Xander lets it slip that Angel was in town.