The mysterious Selena employs Jonathan Steele to protect the staff (entirely female) of the Marine Research Institute, on the small island of Gavdos, in the Aegean Sea. Jonathan, however, receives a rather cold reception, as not even those working at the Institute know Selena or realize that they have become a target of a group of modern pirates. But what are these pirates looking for, and what secret are the girls hiding that Jonathan must protect?