The story begins with Dorothy Gale and her dog Toto. They live on a Kansas farm belonging to her Aunt Em and Uncle Henry. One day, Toto gets into trouble with their neighbor Miss Almira Gulch. The grown ups either don't understand or can't seem to protect Dorothy and Toto from Miss Gulch who tries and almost succeeds in taking the dog away. Tramatized, Dorothy imagines a better, more just world and sings "Somewhere, Over the Rainbow."
Having decided to to run away, Dorothy doesn't notice the approaching storm and is unable to join the others in the storm cellar. When the storm hits, she's struck on the head and experiences a terrifying moment when both she and her house are apparently picked up in the tornado.
When she awakes, she finds herself in Munchkinland in the Land of Oz. There she meets the timid but friendly Munchkinds and Glinda the Good Witch.
Moments later, however, the Wicked Witch of the West arrives looking for her sister, Wicked Witch of the East, who had appently been killed by Dorothy and her falling house. Glinda transfers the ruby slippers to Dorothy's feet before the Wicked Witch of the West could fetch them for herself.
Dorothy is understandably shaken by all of this and asks how she can find her way back to Kansas. According to Wikipedia, "Glinda tells Dorothy to keep the slippers on and follow the yellow brick road to the Emerald City, where she can ask the Wizard of Oz to help her return home. On her journey, Dorothy meets the Scarecrow, who wants a brain, the Tin Woodman, who desires a heart, and the Cowardly Lion, who needs courage. Dorothy invites them to accompany her to Emerald City, where they can also ask the Wizard for help."
At last they're off to see the Wizard.