reading our comments in the official discussion should give you a decent idea of what happened.
Willow goes haywire, and Buffy and Anya rescue Jonathan and Andrew from the jail so Willow can't get them there. They're escaping in a police car, and then Willow appears on top of a truck behind them, controling the truck. But she's drained, and has to refill on magic.
Willow goes to the magic shop, and drains the dark magic books there to get some power. Then she goes to Rack and steals his magic too... Dawn's there (trying to find willow) and Willow does this great scene where she's calling Dawn a whiny little thing and all. Buffy arrives, and she and Willow talk, but then Willow transports the to the magic shop again where Jon and Andrew are now. Anya works a protective spell so willow can't harm anyone, and Jona nd Andrew escape with Dawn and Xander. Buffy and Willow duke it out (good fight scene) then GILES SHOWS UP and puts a binding spell on Willow. He and Buffy go into the workout room to talk, and she tells him what's been going on.. they both start laughing, until Willow comes in the door, freed, (she forced Anya to free her) and she and Giles duke it out while Buffy runs out to save Jon and Andrew again (who are with Xander and Dawn)
WIllow, drained again steals the magic that Giles had (A coven of witches in England gave him their power temporarily so that he could fight willow. So now she has even MORE power... but some of it is "good" instead of the evil that has been consuming her. She can feel the pain of everyone in the world, and deciddes that the only way to end the pain is to end the world (typical, she could just end her LIFE) so she goes to some temple of a she-demon who is hell bent on ending the world and starts feeing the statue power.
Meanwhile, she's trapped Buffy and Dawn underground in the graveyeard where she saved the boys and Xander and Dawn. Xander has disappeared, and the boys are running off to mexico. Buffy and Dawn are being attacked by some weird creatures that Willow sent and Buffy knows she can't take them all by herself, so she asks Dawn to help. Dawn shows off some DAMN NCIE moves... "What? You think I never watched you?" she says.
Giles and Anya are in the Magic Shop... Giles is dying, and Anya is comforting him.
Willow, still feeding the statue power that she takes from the world, is interrupted by Xander who jumps into the beam of power (which stops) He tells her that he loves her, and if the world is going to end, (even if she's the one causing it) then the only place he wants to be is with her because she's his best friend and he loves her. She gets angry and hurts him, but he leeps telling her that he loves her, until she finally breaks down, and he's holding her, and they're both crying and her hair is red again and she's back to being normal Willow.
Giles lives, and tells Anya that XANDER saved the world this time.
Buffy and Dawn climb out of the hole where they were trapped. Buffy tells Dawn that instead of protecting her, she nnow want to show her the world. Hopefully we'll get to see some kickass Dawn fighting next season.
And now you're wondering... what about SPIKE?
the whole episode, Spike has been in Africa seeing this demon thing. He asks the demon to "make him what he was" so that he can show buffy a thing or two. he has to face three challenges, and after beating the crap (and getting beaten himself) out of a few monsters, he again asks the demon to "make him as he was" so the demon says... "I GIVE YOU BACK YOUR SOUL!"
see, the whole time Spike was saying "make me as I was" instead of saying "Take this blasted chip out of my head" and that was the end of it.