Hundreds of years ago, Acathla the demon came forth to swallow the world into the demon dimension. Any non-demon life would suffer horrible…and eternal…torment in that dimension. But a virtuous knight pierced the demon's heart and killed him before he could draw a breath to perform the act. Acathla turned to stone, as demons sometimes do, and was buried where neither man nor demon would want to look. It was said that a special ritual might allow a specific being to remove the sword, thus freeing Acathla to open the vortex to hell once more. Angel believed he was that being. He had been told in the past by the demon Whistler that he would be the one to stop Acathla from rising. The only thing missing was Acathla himself.

But evil always seems to turn up sooner or later. And this evil turned up in Sunnydale. Acathla's tomb was taken to the museum where the curator took one look at it and called Giles. He knew that Giles had been a museum curator in his past and hoped he might shed some light on the strange object. But not long after Giles saw the tomb it was stolen by Angel and his goons, the curator murdered.

While trying to figure out what to do, Kendra the vampyre slayer appeared with a special sword that was blessed by the knight who first slew the demon. Buffy then ran into the demon Whistler who told her that if Angel was successful in freeing Acathla that she would have to kill Angel to close the vortex. Buffy was hesitant because she knew that Willow was attempting to restore Angel's soul. But after Drusilla killed Kendra, put Willow in the hospital and kidnapped Giles (Angel needed his help to tell him what needed to be done to perform the ritual) she knew she had to act fast. But she also knew she couldn't do it alone. But fate stepped in once more and Spike offered to join forces with her in defeating Angel. In return he wanted safe passage for him and Drusilla to leave Sunnydale and never return. Buffy had no choice but to agree.

The plan almost worked, but there were too many vampyres and Buffy was kept distracted while Angel pulled the sword from Acathla. Acathla needed time to awaken though, and during this time Buffy and Angel fought to the death. Buffy was just about to kill Angel when Willow's curse worked and Angel's soul was restored to him. In a bittersweet moment they shared one final kiss before Buffy thrust the blessed sword through him and into Acathla, sealing the vortex to hell once more and sending Angel there for eternity.