The Girl with the Green Tail

Chapter Seventeen: Hermione's Past With Ariel (Part Two: The Switching Spell)

"Caudius aleius corpius..." Hermione said slowly, using her quill to underline the spell in Advanced Transfiguration Spells. "This is it..." Hermione said to herself, "this is what will turn Ariel human! This will allow me to trade my legs for her tail, giving her access to Lavender Brown..."
She checked the clock, thinking it wasn't too late to go find Ariel down at the lake. The clock read 10:38PM. "Surely, it isn't too late..." But then she remembered Filch, and Snape, and her desire to remain without detention or expulsion. She sighed. "I guess I'll have to wait until tomorrow night to talk to Ariel again..."
That night, she began to use the Switching Spell on various objects - replacing the cover of someone's copy of To Kill a Mockingbird (clearly brought by a muggleborn who wanted to read something aside from textbooks) with the cover of another person's copy of Mysteries Untold: What Truly Became of the Pines and the Demon? (unclear to Hermione who brought it, Perhaps it's sold in both Muggle and wizard bookstores? she thought), replacing the fire in the Gryffindor fireplace with a bowl of water on the floor for someone's cat (Heaven's sakes! This was a bad idea! Hermione thought, for the cat that had been drinking the water from the bowl had yowled and ran as its face was submerged in fire, which soon spread across the floor, until Hermione put it out with a simple Water Charm), and finally, to test whether the spell would work correctly, she Switched her legs with the cat's legs (Oh my Merlin! she thought, not wanting to wake anyone, for she had become like a walking Faun, but with cat legs instead of goat legs, and the cat had two human legs for its front legs). She Switched everything back to its original state, and couldn't sleep that night because she was too excited. Her discoveries were amazing! And she was only a first year witch. Wait until I tell Ariel! she thought happily.
Sadly for both Hermione and Ariel, that moment never came.