Valtor decides to attack the star Hypsos, which is located in the star's constellation of the Hydra. When they discover that Hypsos is in danger, the Winx set off on a new mission to save the star. When they arrive on Hypsos, Valtor then uses his powers to turn the constellation of the Hydra into the actual Hydra monster. While the Winx face the Hydra, Musa saves Riven and the two seem to draw closer. The Specialists come to aid the Winx in fighting the Hydra, but it seems nothing affects it.