It has been twelve years since twins Josh and Katie Jenkins were unwittingly propelled into the underwater world of Otriana while searching for their neighbor's dog. After meeting Nepta and his sister, Coralie, who help the twins escape Otriana, their adventures eventually lead them to be accused of murdering Nepta and Coralie's father. Now, Nepta wants to visit the earth world to see the twins again. But there is only one problem: Coralie wants to accompany him and she is out for revenge.
After a merman gives Nepta a bottle of sea wine and a magical ring, Coralie slips on the ring, bringing a pirate captain from the 1740s into the present day to retrieve his beloved ring. When they manage to escape with ring in hand, Nepta and Coralie meet up with the Jenkins' twins and their younger sibling, Kyle. Now together with help from several companions, Nepta journeys through an unforgettable adventure where he must learn how to properly use the ring to banish the pirates forever.
In this entertaining young adult fantasy, young earthlings and their underwater friends continue their escapade through sea and land where good battles evil and the past confronts the present.