I promised a summary of Wicked, here it be (!SPOILERS THOUGH!):
The show opens with the citizens of Oz rejoicifying at the death of the Wicked Witch of the West at the thirteenth hour according to the Time Dragon Clock due to a bucket of water thrown by a girl. Glinda the Good comes and affirms the death of the Witch. When someone asks about wickedness,Glinda explains that the Witch had a family and childhood, but themother had an affair with a travelling salesman who gave the mother a drink from a green elixir, thus turning the child in the mother's womb green. When the child is born, the mother's husband shuns the baby. When Glinda finishes, the citizens don't seem to care much. Glinda then begins to leave when someone demands to know if Glinda and the Witch had been friends. Glinda says this is true, but "It depends on what you mean by friend. I did know her. That is, our paths did cross...at school..."
Elphaba Thropp appears at Shiz University where she is immediately shunned because of her green skin. Her wheelchair bound sister Nessarose is then wheeled in by their father. The father gives Nessa a pair of jeweled shoes and tells Elphaba not to talk so much. Madame Morrible, headmistress, comes in and speaks with the students. A twist of fate lands Elphaba and Galinda together as roommates. When Elphaba protests, her gift with magic is revealed and Morrible is ecstatic and tells Elphaba that she could meet the Wizard.
Meanwhile Elphaba and Glinda are happily loathing everything about each other. After a disturbance in history class, taught by a Goat named Dr. Dillamond, a Winkie Prince, Fiyero, shows up at Shiz and teaches his classmates how to live by "Dancing Through Life". AMunchkin named Boq tries to go with Galinda, but she manipulateshim into taking Nessa. As everyone preps for the party, Galinda is egged on by her friends to give Elphaba a "hideodous" black conical hat. Elphaba accepts the hat, thinking it is a sign of friendship from Galinda. During the party, Morrible shows up and give Galinda a training wand, saying that Elphaba had insisted upon it. This makes Galinda feel terrible, even more so when Elphaba shows up at the party wearing the hat. As Elphaba dances alone, Galinda joins in and people begin to accept Elphaba.
Back in their room, Galinda tells Elphie that she is going to marry Fiyero, even though he hasn't asked or knows. Elphaba then tells Galinda a secret about how her father blames her for Nessa's condition. Their father made their mother eat milkflowers during her pregnancy with Nessa which caused her to be born too early and their mother never woke up. Galinda assures that it was not Elphaba's fault and then gives her a makeover. The next day in class, Dillamond is removed, yelling about how the students are not being told the whole story. The new professor comes in with a caged Lion cub and Elphaba grows too angry. Everyone but her and Fiyero are affected and they spirit the cub away. The two make it to the safety underneath a bridge and begin talking. Fiyero and Elphie seem to be falling for each other, but Fiyero runs off with the cub, leaving Elphaba to think of what could be. Morrible then appears with exciting news: the Wizard wants to meet her.
At the train station, Boq tells Nessa he can't be with her and runs off. Galinda tries to tell Nessa that maybe he isn't the right one, but Nessa is insistent and leaves. Fiyero comes and bades Elphaba farewell. Galinda tries to jump in as they talk about Dillamond and declares that she will be called Glinda now (since Dillamond couldn't pronounce Galinda). Fiyero doesn't seem to care and leaves. Glinda then begins sobbing and Elphaba persuades her to go to the Emerald City with her. After walking around the city, they meet the Wizard and his new Press Secretary (Morrible), who has the Grimmerie. They tell Elphaba to cast a levitation spell on Chistery so he can fly like the birds he watches. Elphaba complies only to realize with horror that she's been tricked into giving a large cageful of monkeys wings. She realizes that it is the Wizard who is causing the Animals to revert into non-speaking animals. She runs off with the Grimmerie. Glinda follows saying she'll fetch her friend back.
The two friends arrive in an attic and Elphaba bars the door with a broom. They begin bickering only to stop to listen to Morrible's announcement about Elphaba being a Wicked Witch. Elphaba ignores her friends pleas to apologize and enchants the broom to fly. She tries to get Glinda to come with her, but the blonde won't. They say goodbye and Elphaba flies off to the west.
Act two opens several years later with the citizens of Oz talking about how wicked Elphaba is. Glinda, Morrible, and Fiyero, the new Captain of the Guard appear and reassures the citizens not to worry. Fiyero then learns that it is an engagement party. As Morrible recounts what "really" happened in the Wizard's throne room, citizens began spreading rumors. Fiyero leaves when someone claims water will melt Elphaba. Glinda makes up a story to hide Fiyero's sudden departure.
Meanwhile, Nessa is being attended to by Boq. He leaves the room. As Nessa looks at herself in a mirror Elphaba appears out of the closet, startling her sister. She tries to get Nessa to ask their father for help and is told it is impossible. Their father is dead, "Embarrassed to death." When Elphaba tries to get Nessa to help her, the crippled sister refuses, accusing Elphaba that she cares more about nameless Animals than her own sister. Elphaba begins to say something when she gets an idea. She casts a spell on the jeweled shoes and they allow Nessa to walk. Nessa calls for Boq who is stunned to see Elphie. When he learns that Nessa can walk, he begs her to let him leave so he can stop Glinda's engagement. Nessa is furious and casts a spell from the Grimmerie so Boq will lose his heart to her. Elphaba tries to stop her, telling Nessa she's pronouncing it wrong when Boq shouts his heart is shrinking. Elphaba quickly grabs the book, saying their is no reversal of a casted spell. She finds another spell and leaves. When Boq awakens, he and Nessa are mortified to find that he is made of tin. He runs out, Nessa shouting that it was Elphaba's fault.
In the EC, Elphaba is looking around for the cage of the Flying Monkeys. The Wizard appears and persuades Elphaba to join him. She agrees on the condition that he frees the Monkeys. He complies. As Elphaba watches them fly away, she notices a shape under a blanket. She goes to investigate and before the Wizard can stop her, she discovers that it is Dillamond, reverted completely into a goat. Elphaba tells the Wizard she will fight him to the day she dies when Fiyero and two guards come in, one claiming "There's a goat on the lam". Fiyero ignores the remark and orders them to get water. Once they are gone, he pulls the Wizard out from his hiding spot. Glinda comes running in and is happy to see her friend alive. She is stunned to see Fiyero holding a gun on the Wizard and is even more stunned when he says he is leaving with Elphaba. The two women are stunned and Elphaba and Fiyero leave before more guards come. The Wizard offers Glinda a drink from a green bottle as Morrible comes in. As they discuss ways to flush Elphaba out, Glinda tells them to use a rumor about Nessa. She then leaves. Morrible agrees that Nessa is the key, but a rumor won't do it, but perhaps "a change in the weather" will.
Elphaba and Fiyero escape to a forest where they confess their love for each other. Elphaba then sees a house flying through the sky and knows that her sister is in trouble. Fiyero tells Elphaba his family has a spare castle called Kiamo Ko that is full of trapdoors and secret passageways. She runs off to help her sister.
Glinda is calling down the Yellow Brick Road to Dorothy, hoping that they don't get lost. She then pays her respects to Nessa when Elphaba appears from a cornfield. The two begin bickering and begin to fight when the Wizard's Guards run in and capture Elphaba. She is stunned and hurt that Glinda could do such a thing (even though she didn't) when Fiyero swings in, gun aimed at Glinda. Elphaba is released and reluctantly leaves. The guards then string Fiyero up on some poles in the field until he tells them where Elphaba went. At Kiamo Ko, Elphaba tries to cast a spell to save Fiyero. She believes it doesn't work and finally accepts her title as wicked.
Back in the EC, Boq the Tinman tells how he and the Lion have a score to settle with Elphaba. Glinda finally realizes what is really going on and runs off to Kiamo Ko. As she arrives, Elphaba is snapping at Dorothy to give her the jeweled shoes and is trying to get Chistery to speak. Glinda appears on a stairwell and begs Elphie to let the girl go and "Dodo too" (Glinda's bad with names). Elphaba begins to refuse when a Flying Monkey hands her a piece of paper. Glinda guesses it has something to do with Fiyero. Elphaba says they've seen his face for the last time and gives up. She hands Glinda the Grimmerie and the two reaffirm their friendship.
As the Witch Hunters storm inside the castle, Elphie hides Glinda where she watches her friend melt. When everyone except for her and Chistery have left, she emerges and picks up her friend's hat. Chistery notices a green bottle and hands it to Glinda. Glinda studies the bottle and heads for the EC where she confronts the Wizard. She shows him the bottle and realization that Elphaba was his daughter sinks in. Morrible realizes that that was how Elphaba had such power: she was a child of both worlds. Glinda forces the Wizard to leave and imprisons Morrible.
At Kiamo Ko, the Scarecrow stumbles around and kneels down where Elphaba melted. He bangs on the door, saying it worked. He opens the trapdoor and Elphaba comes out. Realizing that they must now leave Oz, she says one final goodbye to Glinda, who truly wants to be Glinda the Good. She and Fiyero then leave through the Time Dragon Clock.
And that's the summary...a bit long...but a lot happens...hope that helps explain some stuff for some.