Cordelia is in a stroppy mood after a series of mishaps and blames it on one Buffy Summers. When demon Anya, making her debut in the series, overhears Cordelia say that she wishes Buffy never arrived in Sunnydale - she grants the wish courtesy of an amulet. Subsequently, history is rewritten accordingly and the town is overrun by conflict and evil that has emerged from underground. This also paves the way for the return of the original Big Bad - The Master. Xander and Willow are now bloodthirsty vampires.
As Rupert Giles battles the demonic Anya, the alternate universe is overrun with fierce fighting between a series of familiar figures in a warehouse. Buffy, having arrived from Cleveland, is on the warpath but obviously doesn't recognise people like Xander and Willow.
Shortly after staking Angel, Xander - in glorious slow-mo - heads over to Buffy and takes a swing at the slayer. She blocks his punch and nonchalantly stakes him in the heart. With one final look of anguish, Xander turns to dust and Buffy stomps away. Although not taking place in the 'real' universe, it's nonetheless unsettling to see two such loveable characters locking horns.
Buffy's neck is snapped by The Master shortly she kills Xander, but Giles manages to make Anya reverse the spell and normality is restored. However, the demon returns several episodes later and manages to drag the alternate sexy vampire Willow into the real world as she bids to regain her powers. Despite her devious origins on the show, Anya quickly becomes a series regular and Xander's love interest.