Jean, Nadia, and King are shot down over a strange island where they find themselves outrunning a squadron of sinister masked soldiers. In their struggle to survive, they find an orphan girl, Marie, who lost her parents to the soldiers.

The Nautilus is ensnared by Gargoyle's super powerful SeaNet magnet. In the fight that follows, Grandis, Sanson and Hanson escape on the Gratan (to help free Nemo and the others from Gargoyle's battleship). The battle culminates with the badly damaged Nautilus plummeting into the sea....

Finally, our pals arrive at Nadia's real homeland--Tartessos. As they tour through its long forgotten ruins, our heroine finally reveals her darkest secrets... including who she is. How will all this affect her relationships with everyone, especially Jean?