I Only Have Eyes For You
On the night before the Sadie Hawkins dance, Buffy is heading towards the library, only to encounter a boy about to kill a girl with a gun. as soon as Buffy knocks the gun from his hand, though, both of them regain their senses - the pair have no idea why they were fighting - and the gun disappears. Later, in Principal Snyder's office, something knocks the 1955 yearbook off the principal's shelf in from if Buffy, and then while bored to tears in history class, she gets a vision from the '50's of a Sunnydale High student named James and a teacher named Miss Newman, who seemed to have a relationship.
Strangeness continues as Xander is attacked by a dessicated arm in his locker, snakes start to appearing in the school and the janitor and a teacher play out the exact same scene as the two students did earlier - but without Buffy to interfere, the scene results in the janitor shooting the woman. Willow discovers the story of James and Miss Newman, who had an illicit affair in 1955, and on the night of the Sadie Hawkins Dance, he killed her and then shot himself in the head. The Slayerettes figure it's a poltergeist: James' spirit trying to resolve the conflict. An attempt at an exorcism fails, and finally the spirits confront each other yet again - this time with James inhabiting Buffy and Miss Newman inhabiting Angel.