In the season 2 finale, when Buffy is going to stop Angelus from awakening Acathla, Willow decides that she should try to help out by casting the ritual to restore Angel's soul. Since Willow's in a hospital bed and Giles has been kidnapped, she sends Oz and Cordy to get the necessary stuff and Xander to intercept Buffy and tell her what Willow is up to. When Xander catches up with Buffy, he declines to tell her. This then leads to Angel getting his soul back way too late, when the only thing Buffy can do to close Acathla's hell-vortex and save the world is to stab Angel through the heart, which means that the vortex sucks Angel into hell just as it closes. It's one of the saddest moments in the whole series.Valanthe the Sleepless said:Angelsboi - What did Xander do to betray Buffy? I am a little sketchy when it comes to the first 2-3 seasons.