Rita and the girls worry about the upcoming full moon's effect on Zac. Nixie thinks they should let Zac find the trident so they can take it from him and hide it. Lyla thinks they should come clean with him so he'll in hopes that he'll understand and stay away from it. While Lyla warns Zac to keep away from Mako Island during the full moon, Evie sees them holding hands and breaks up with him. Cam discovers that the girls know Zac's secret but feels uneasy about them helping him. Under the light of the full moon, Zac goes after the trident with the girls close behind.
Nixie and Sirena won't help Lyla try to "zap" Zac's powers, so Lyla decides to do it alone. This misfires when a waitress spills a drink on Lyla and Lyla rushes to hide in the refrigeration room before she transforms into a mermaid! When she can't dry her tail, Nixie and Sirena must save her before she is discovered!
It's a full moon and the three mermaids Nixie, Lyla and Sirena are tasked to guard Mako and the moon pool. While Zac and Cam go camping on Mako island. When Zac falls into the moon pool they don't know what to do and leave him on the beach. The next day Zac finds out what he is and what he can do so he tells Cam. Because the girls let the "land boy" as they call him in the moon pool they are being cast out by their pod. So they decide to fix the problem.