The Winx change their concert into a benefit concert to help clean up the oil spill. Tritannus escapes from prison with the help of the Trix and begins absorbing the pollution from the oil spill allowing him to transform into a monster. The Winx find that the Trix have escaped from prison and that a mutated monster has control of the Gate from Andros to Earth. Aisha learns that the monster is her cousin, Tritannus. Flora, Tecna and Aisha find that it is difficult to swim underwater with their Believix powers and their magic does not work well and is less effective under the ocean either.