The story begins with the evil fairy Maleficent crashing the celebration of Princess Aurora's birth, where she gives her the gift that keeps on giving: A curse that will cause her, on her 16th birthday, to prick her finger on the spindle of a spinning wheel and die (spindles were basically the medieval equivalent of a modern public bus seat). Three good fairies, Flora, Fauna, and Merryweather "help" the princess by adjusting the curse so that she won't die, but merely sleep forever, because they're firmly against DNRs and can't help but inject their politics into their magic. Then they whisk the child away to raise her in the woods, in a shack, destitute, with no magic, even though the curse only put her in danger for one single specific day out of 16 entire years. The king and queen agree to this plan because they were apparently hoping for a boy, anyway.
Fast forward 16 years, and we find the fairy trio having a noisy and colorful magic-off to celebrate the princess' birthday -- on the one and only day they had to be discreet.
"Just for once, can you guys just be cool?"
Maleficent finds Aurora and sees her curse through. As the three fairies cry and wail over the princess' easily avoidable coma, Merryweather says, "[The king and queen] will be heartbroken when they find out." To which Flora responds, "They're not going to. We'll put them all to sleep, until she awakens."