The archenemies of the Winx Club, the Trix witches, team up with the evil nymph Politea and find out that, to defeat the fairies once and for all and become invincible, it takes very little: a Pearl hidden in the Deep of the Infinite Ocean! As small as powerful, the Pearl of the Depth gives enormous powers to those who possess it! For the Winx there is not a minute to waste: how will they stop the plans of their enemies before it's too late? Get ready: the most dangerous mission of the Winx is about to begin!

School for fairies Alfea celebrates the inauguration of the new school year when the party is interrupted by Icy, Darcy and Stormy, the perfidious Trix. The Winx without Bloom, are forced to remedy the confusion created by the witches who, having ruined the party, steal a powerful and mysterious object. Meanwhile, Bloom is on Domino, which is experiencing the best moments of his new life as a princess. He finally found his parents and Sky asks her to marry him. But not all gold that glitters, the three Witches are Ancestors in fact come back to haunt Stella, Aisha, Tecna, Musa, Flora and Bloom. Moreover, Erendor, Sky's father, forbids his son to marry the princess of Domino. A dark secret lies in the realm of Eraklyon and now that Sky, the legitimate ruler of the kingdom, as known.

Sixteen years ago the most powerful warrior wizards of the Magic Dimension sacrificed themselves to fight against absolute evil. Now the fate of a kingdom is in the hands of a young girl - Bloom, the fairy of the Dragon's flame. Accompanied by her Winx Club girlfriends, Bloom must overcome the greatest challenge of all: enter the depths of the obscure dimension, fight against evil to bring her parents back to life and reveal the mystery linked to her origins. The destiny of the entire Magic Dimension depends on the outcome of this conflict.

In a magical universe, witches, warriors begin fighting in the name of good .vs. evil! At a magic school, five teenage girls are selected to defend the universe with their magic.