After Mylie, a mermaid turned human makes a deal with a sea-hag, she turns to Piper, Phoebe, and Paige after their pact turns out bad. As a result of the sisters' helping her out, Phoebe gets turned into a mermaid. Meanwhile, as this is playing out, Phoebe's divorce of Cole gets put on hold when he returns, begging her to take him back. Cole then decides to help Daryl out in an attempt to get back on Phoebe's good side. As Paige struggles to find a balance between her work as a Charmed One and a Social Worker, Piper struggles to face her fears of a water demon.

A wicked witch breaks free of the confines of the mirror after she kills the Keeper of the Fairy Tales and sets her sights on destroying Piper, Phoebe, and Paige. As a result, Piper and Grams fall victims to Wolf from Little Red Riding Hood, Phoebe to the glass slippers found in Cinderella, and Paige to the poison apple from Snow White. It takes Cole and Leo working together to find a way to vanquish the wicked witch, break the evil spell over the fairy tales, save the sisters, and set the fairy tales back to how they were originally written.