Buffy's faced many challenges but now she faces her biggest test yet - caring for her younger sister Dawn, as her mother receives treatment for a serious illness.

Dawn is a new character in the Buffy universe, but Buffy and the gang act as if she's always been there. It soon becomes clear that Dawn's sudden arrival is part of the storyline - and Buffy comes to suspect that her own sister is not what she appears. But who's been messing with everyone's memory, and why?

This season includes some disturbing moments, as Buffy's mother Joyce suffers from a brain tumour which causes her to behave erratically. Meanwhile, the season's villain, Glory, is brilliantly portrayed as a supremely powerful version of the fashion-obsessed valley-girl Buffy might have become in an alternative life.