In The Wizard of Oz, Dorothy needs the ruby slippers to get home. The witch is desperate to get her hands on them, too, for their magic powers. But she has to kill Dorothy to get them.
In the original L. Frank Baum novel, they're not ruby slippers. They're silver shoes (not as photogenic, I'm sure the folks at MGM said). This W. W. Denslow illustration from the book's first edition (1900) shows the moment when the witch has already stolen one of the silver shoes, so Dorothy fights back, chucking a bucket of water over her.
Here's how the novel ends:
Dorothy now took Toto up solemnly in her arms, and having said one last good-bye she clapped the heels of her shoes together three times, saying:
"Take me home to Aunt Em!"
Instantly she was whirling through the air, so swiftly that all she could see or feel was the wind whistling past her ears.
The Silver Shoes took but three steps, and then she stopped so suddenly that she rolled over upon the grass several times before she knew where she was.
At length, however, she sat up and looked about her.
"Good gracious!" she cried.
For she was sitting on the broad Kansas prairie, and just before her was the new farmhouse Uncle Henry built after the cyclone had carried away the old one. Uncle Henry was milking the cows in the barnyard, and Toto had jumped out of her arms and was running toward the barn, barking furiously.
Dorothy stood up and found she was in her stocking-feet. For the Silver Shoes had fallen off in her flight through the air, and were lost forever in the desert.
Chapter 24 - Home Again
Aunt Em had just come out of the house to water the cabbages when she looked up and saw Dorothy running toward her.
"My darling child!" she cried, folding the little girl in her arms and covering her face with kisses. "Where in the world did you come from?"
"From the Land of Oz," said Dorothy gravely. "And here is Toto, too. And oh, Aunt Em! I'm so glad to be at home again!"
So what do ruby slippers have to do with writing a crime novel?
For me, they're a plot device, like Hitchcock's MacGuffin, a tangible object of desire that competing characters will do anything to obtain or protect or hide or destroy.
Single object; competing goals. Like the statuette in The Maltese Falcon. Or the Degas painting in The Art Forger. Or Tara in Gone with the Wind. Or the postage stamp in The Sweetness at the Bottom of the Pie. Or Katniss Everdeen's pin and the freedom that it represents in Mockingjay.
Not every novel has ruby slippers, but each time I develop a plot, I try to find my story's "ruby slippers" -- a single object that either embodies (like Dorothy's ruby slippers) or represents (like Katniss's pin) what the protagonist and villain are competing for.
In my novel Never Tell a Lie the ruby slippers is an unborn baby, and also an inherited necklace that goes missing at the start of the book. In the novel I just turned in, You'll Never Know, Dear, it's a porcelain portrait doll and the little girl who disappeared with it.
Thinking about the plot devices in books you've read or written, are there any examples of "Ruby Slippers?"