Under the full moon, the girls' powers are enhanced and wreak havoc on Lewis in his boat, and the next day the girls realize they still need Lewis.

Emma uses her powers to help Elliot at soccer; Lewis decides to test the girls' increased powers; Cleo hates Lewis's smothering and dumps him.

Zane's back in town and still in love with Rikki, and works out she's still a mermaid and tries to win her back; Cleo becomes suspicious of Lewis.

In trying to compete with Rikki, Emma tries to rebel and throws a party; Nate uses Lewis to make a play for Cleo.

Lewis and the girls make a potion supposed to allow the girls to grant wishes. Wilfred worries he will have to close the Juicenet Café, and Emma suggests they make a TV commercial.

Cleo is worried when she sees her dad around with another woman. When she arrives at their house, she turns out to be Charlotte's mother. Meanwhile, Rikki and Emma attempt to save the Sertori's dinner with their powers.

Everyone is shocked when Cleo is fired at the Ice Cream Stand, and even more so when Lewis takes her place. Rikki and Emma strike back at him but end up going too far

Zane is curious by Rikki's reluctancy to reveal where she lives. So one day, he eventually convinces her to reveal her home: a trailer park with her grouchy father.

Emma has to take Eliot for horse riding lessons and the competitive perfectionist tries to be better than the instructor. Meanwhile, Lewis double dates with Charlotte and Cleo.

Cleo starts to struggle at school and gets help from the new tutor. But there are bigger problems when Charlotte starts to get closer to Mako Island with the help of Lewis.

In need of cash, Rikki decides to go and searching for a lost statue with a huge reward. But she lies to Emma and Cleo, which causes danger when Rikki is knocked out.

Emma gets poisoned after cutting her finger on some coral and she begins to turn into a white scaled monster. Meanwhile Charlotte thinks Cleo is trying to break her and Lewis apart.

On the night of a full moon, Lewis, Emma, Rikki and Charlotte accompany Cleo's family for a camping trip at Mako. When all three girls are affected by the moon, they are unable to stop the curious Charlotte.

Cleo decides to restart her friendship with Lewis and embrace her abilities, while Emma is shocked with the new supervisor who has big changes planned.

Zane learns of the myth of Ambergris, a fragrance that can make mermaids fall for any man that wears it. When he buys it, Nate ends up wearing it and Emma, Cleo and Rikki all fall for him.

Lewis keeps dreaming that Cleo is discovered to be a mermaid. Elliot has a crush on Kim and she agrees to go on a date with him to the marine park. Don makes Cleo chaperone. Emma is suspicious of Rikki and Ash's private conversations.

The girls prepare for the full moon again and insist they don't need Lewis' help. Rikki and Cleo suggest Ash to be more bold with Emma. Following their advice, Ash decides to do a surprise visit which could uncover their secret.

Cleo plans a party at the moon pool to celebrate the one year anniversary of the girls becoming mermaids, but when Zane and Ash have an argument at the juice bar, Rikki and Emma take sides against each other and forget about the party.

Lewis is trying to find more information on the moon pool and stumbles across research on it by Max Hamilton from fifty years ago. Will Lewis reveal the girls' secret to him in order to complete the puzzle?

Charlotte wants answers as to why Lewis is spending so much time with Cleo and the girls.

Charlotte's stubborn nature and thirst for knowledge leads her to Max, who confirms her suspicions and leads her to the Moon Pool. Lewis meanwhile is having trouble trying to keep their relationship together.

The girls decide that they should accept Charlotte, and the four work together when they need to join the volleyball team to avoid failing Physical Education.

Charlotte is determined to prove her love for Lewis and show she is better than the other three, and refuses their advice and takes matters into her own hands when Nate causes trouble for Lewis.

More friction arises, this time over Lewis' birthday party. Charlotte takes control and drives Rikki away from the party. However, things go out of hand and it is up to her to save the day.

Charlotte's short-lived friendship with the other girls is over and she demands that out of loyalty to her, Lewis have no further contact with Rikki, Emma and most of all, Cleo.

Lewis find out that there is a way for a mermaid to lose her powers and attempts to lure Charlotte to the Moon Pool. The plan backfire and it looks like all the girls may lose their powers.