Tritannus raids King Neptune's underwater palace and transforms his entire family into mutants. Then he absorbs the power of his dad's mystical sword. Meanwhile, Musa, Aisha, and Stella get a second clue to Sirenix which leads them to Musa's home world, Melody. Searching for the Gem of Empathy, Tritannus transforms Musa into a monster and she is saved when she bonds with the Selkie who guards Melody's ocean gate, Sonna. Meanwhile, the Trix and Tritannus reach Daphne in Lake Roccaluce, and capture her.
