Nettie Pearlman's normal life is flipped upside down when four mysterious lights fall to her island home. She goes to investigate, but the lights also catch the attention of a young Pirate.
Nettie meets four lost mermaids looking for a lagoon to call home, and she's eager to assist. Before Nettie can start helping her new friends though, a sea monster appears and comes after the mysterious mermaids.
Hoping they'll help find the Lost Girls a new place to live, Nettie visits her father and grandmother in the Undersea Palace. Her grandmother has an old story for her though that might take Nettie by surprise.
Jacquotte and her Zombie Crew confront Nettie and the Mermaids on the desert island, facing off in a beach-side sword fight. Afterwards, Nettie seeks out help from Calypso's Sea Goddess sisters.
After helping Iris out with a bit of mermaid magic, Nettie and her friends dance the night away at the Hibiscus Cove Founder's Day Ball! This night isn't all fun and games though, as the Ball's Guest of Honor makes a startling realization.
Mermaids have disappeared, pirates are dealing with sea witches, and now Hibiscus Cove is in danger. Nettie will have to have faith and trust in herself as she confronts the biggest danger yet.