History A pod consisting of over a hundred mermaids took refuge on the reef of. Sirena, Nixie, and Rita attempt to use their Moon Rings to heal Lyla, but this fails when the rings run out of magic. Sirena reveals to Zac, Ondina, and Mimmi that she has kept the stone hidden at Rita's grotto the entire time. The next day, Veridia lifts the girl's banishment and informs them that the pod will return by the next full moon. However, with Cam's help, Zac evades the girls and finally gets possession of the trident. When Zac experiments with a stone carving in the chamber, Ondina suddenly disappears.
The two find Zac, Erik, Ondina, and Mimmi at the currently active chamber. Together forever together lying in the sun. Afterwards, Ondina and Mimmi reconcile with Ondina promising never to let Erik come between their friendship. But when Sirena mentions that Rita was once her teacher, Ondina arrogantly claims Rita's teaching methods are outdated. A young mermaid, named Neppy, follows Ondina back to the mainland, inspired by Ondina's dedication and wanting to help her save Mako.
He races to Mako Island to get the trident, with the girls in hot pursuit. In the process, Mimmi and Rita are splashed and Zac and Evie are forced to drag them to safety. . Evie overhears this and is greatly touched. Erik's interest in Ondina continues to grow. Sirena believes that the time has come to tell him the truth, but the other mermaids forbid it. Ondina apologises to Neppy and takes her back to the pod.
With the full moon approaching, Ondina tries to warn Erik not to activate the merman chamber, but Erik refuses to listen even to her. Erik finds a pearl and gives it to Ondina as a gift. Though Sirena is reluctant to leave her two friends, they both insist that she go. When she does, he not only promises to keep her secret, but reveals that he is a merman and that his kind live primarily on land and travel frequently to keep their secret. Fortunately, Ondina and Mimmi are able to break the spell by singing a counter enchantment song. Carly witnesses one of the sneezes and becomes suspicious that Evie is hiding something from her. When a couple of jerks show up and ridicule Zac by calling him a quitter, Zac becomes very angry and begins recklessly using his powers against them.
As Neppy begins to question Ondina's dedication to Mako, she loses her temper and hurts Neppy's feelings. Rita realizes that their only hope of saving Lyla rests with using the trident to recharge the Moon Rings. They and Rita are approached by Veridia, the head of the mermaid council. However, the girls see through Cam's deception and realise what Zac and Erik are up to. Nixie becomes despondent when she realizes their pod may never return and isolates herself from Sirena and Lyla. The girls take the fish bowl to the party unaware that Evie is inside.
Erik decides to come on the trip as well so he can learn more the island. At the Moon Pool, Ondina runs into Veridia who has come up with a plan to destroy the chamber by having Ondina use her power to turn the chamber's power against itself when Zac activates it. An angry Veridia brands Mimmi and Ondina as traitors and banishes them from the pod. Zac is determined to return to Mako Island and, against Nixie and Sirena's advice, Lyla decides to help him, believing if they can discover how Zac got his powers, they can learn how to take them away. In this world we're all alone, You know I love my island home. Sirena implies to him that she will one day tell him the truth. Ending version: In this world we're all alone You know i love my island home.
Realizing the stone is not safe with him, Zac turns to Cam and asks him to hide it. The girls soon realize that having legs is quite different than having a tail. Cam rushes back to land and asks Zac and the three mermaids for their help to rescue Erik. But Zac's connection to Mako is growing stronger. She realizes Sirena is under the spell of a northern mermaid siren song that affects men and southern mermaids. I look forward to reading yours.
Zac finally realizes how dangerous the trident truly is and returns it to its resting place on Mako Island, ending his feud with the mermaids. Their legs would allow them to walk on land and use their powers on him when he least expects it. To cheer Evie up, Mimmi lets her try on her moon ring. A now powerless Zac has seemingly given up despite encouragement from Mimmi, Evie, and Cam. Meanwhile, Zac learns that the object he saw on Mako Island was a trident and does some research on it.
Later at the cafe, Cam takes some unwanted pictures of Nixie, annoying her and causing her to throw the phone aside and it gets lost somewhere in the cafe. Erik tries to bribe Cam into giving him the stone but Cam refuses to lose his friendship with Zac twice and, instead, gives it back to the mermaids. However, Mimmi and Ondina are concerned about Zac being at Mako. The girls confront Zac in the grotto and inadvertently charge the trident when it suddenly begins absorbing energy from Sirena's Moon Ring. Afterwards, Cam tells Nixie that he also wants Zac back to normal and offers to help her. Meanwhile Sirena and Mimmi create a body lotion that moisturises the applier's skin and makes them look younger.
Their worries are proven correct when the water soon begins to have unpredictable effects. Their boat's anchor gets stuck forcing them to swim to the island and await rescue. David goes out for some training and leaves Carly in charge of the cafe. They share a kiss and become a couple. While Lyla advises Zac to avoid Mako Island throughout the full moon, Evie sees them holding breaks as well as hands up with him.