Dr. Denman has discovered the girls' powers and traps them at the Moon Pool. Zane proves where his loyalties lie when he finds out, but as Denman won't forget about the girls, their only hope seems to lie in the coming night's lunar eclipse, which will take away their powers...
With the school dance coming up, Emma and Cleo hope Byron and Lewis will ask them out. Meanwhile, Miss Chatham and Lewis are arguing about which is more important, magic or science.
Lewis enters the annual fishing derby. When Cleo sees him struggling, she decides to help him out with disastrous consequences. Meanwhile, Rikki and Zane are trapped on a hotel balcony.
The full moon has come again, and the girls are taking every precaution they can imagine this time. It proves to be in vain, however, when Rikki falls under the spell.
A thunderstorm rolls in, leaving the girls little choice but to feign illness to avoid blowing their secret. However, their facade attracts far too much attention, and there might be only one solution for escape...
Emma invites Miss Chathams to stay at her place and Zane overhears Miss Chathams concerning about 'her treasure'.
Byron asks Emma for help with training the school's swimming team and Emma has some trouble deciding whether or not to help out in her current situation. Meanwhile, Lewis continues to experiment on the girls, which annoys Rikki.
Rikki, Emma and Cleo discover that sea turtles are being captured by fishing nets. When Rikki and Emma attempt to rescue the turtles by cutting the nets, it causes the fisherman to think that there is a rogue shark roaming their ocean.
This a feature length movie compiled from 7 first-season episodes, which shows how it all began for Cleo, Emma and Rikki and some of the ups and downs of their adventures.