In the abnormally brownish land of Kansas, young Dorothy Gale (Judy Garland) runs into problems with local Horrible Person Miss Gulch (Margaret Hamilton). She insists on taking Dorothy's dog Toto off to be euthanized because he's been chasing her cats.
So far it doesn't sound like a movie that'll turn into a classic, but...we'll wait.
Toto escapes, but since Dorothy's Aunt Em (Clara Blandick) and Uncle Henry (Charley Grapewin) basically stood there wringing their hands while the poor little guy got loaded on the Put-to-Sleep Express, Dorothy decides to hit the road.
The kindly Professor Marvel (Frank Morgan) guides her back home just in time for her to take a tornado ride to a colorful, magical land of giggling little people. Her house lands on the local wicked witch, making her a national heroine and gaining the enmity of Witch 2.0 (also Hamilton) who covets the magical ruby slippers that mysteriously migrated from the dead witch's feet to Dorothy's.
The good witch Glinda (Billie Burke) appears and advises her to revisit that "hit the road" plan and make her way to the Emerald City, where the mysterious Wizard of Oz can get her out of this extended hallucination toot-sweet and send her back home. The Yellow Brick Road points the way and leads her to a motley crew:
They get to the Emerald City after dodging some threats from the Wicked Witch of the West, only to watch the bottom drop out of all their plans. A very scary Wizard (also Morgan) demands the witch's broomstick in payment, sending them off to the deep dark woods and a passel of flying monkey minions ready to rumble. Dorothy gets dragged back to the witch's castle with her friends in hot pursuit. They save her just before the sand runs out (literally), but the witch corners them and prepares an uncomfortably ironic demise for each one.
Dorothy responds by throwing a bucket of water on her—though actually she just wanted to save the scarecrow after the witch set him on fire—and the villainess's secret weakness is revealed. (Wow, troubles do melt like lemon drops out here.) The witch's henchmen were apparently getting ready to give her a World's Worst Boss award, and set the foursome free with a hearty "thank you so, so much!" and a joyous rendition of "Ding, Dong! The Witch is Dead!"
We know you know all the words.
They take the broomstick back to the Wizard, who suddenly gets a case of the Wait-A-Minutes instead of granting them their hearts' desires. They get pretty angry at him (having just iced a Wicked Witch, the Wizard's whole giant-head-and-billowing-fire routine doesn't look all that menacing anymore), and Toto knocks the whole apple cart over by pulling away a nearby curtain to reveal a nervous little man running a giant Wizard apparatus.
As it turns out, he's the Wizard: a huckster with no powers and abilities, surviving on his ability to put on a great show and nothing else.
(Yep. That's where the phrase "the man behind the curtain" comes from.)
After a few half-hearted apologies about sending them off to their deaths, he produces a series of objects designed to make the gang feel better: a diploma for the scarecrow, a heart-shaped watch for the Tin Man, and a medal of valor for the Lion.
Dorothy, unfortunately, can't solve her problem with a trinket. So the Wizard agrees to take her home in a balloon, the same one that brought him here. Sadly, Toto's cat-chasing habit gets the better of him, and Dorothy gets out to chase him. By the time she gets him, the balloon has broken loose and goes flying off into the sky without her.
All seems lost until the appearance of Glinda, who reveals that the magic shoes can take Dorothy home whenever she likes. She says a tearful good-bye (while classily declining to mention that Glinda could have told her this at the start of the movie), and then returns home to find friends and family waiting for her.
There's no place like home.