Nina and her friends continue the fight against the evil magician Karkon and his minions. This time, in search of the Third Secret, the guys go to Mexico, where they have to fight with the mayor of Venice LSL, who also turns out to be a Black Magician and takes the form of a Feathered Serpent. The main action takes place in Mexico on the ruins of Mayan pyramids. All the mayor's power and black magic fall on Nina. The ancient Mayan god Yum-Ka comes to her aid. But the Feathered Serpent manages to cast a spell on Nina.