Emma, Rikki and Cleo think they fooled everyone who discovered their secret into thinking they lost their powers. Only Lewis knows they re still mermaids. Life is back to normal for the girls, they go swimming on the under... more »water reefs, shop for the latest clothes and avoid getting splashed with water. After all, no-one wants to grow a mermaid tail in public! Life radically changes on the next full moon when the girls are hit with a super strong moon blast that sends their powers out of control. Lewis is almost hurt as the girls struggle with their powers over water. However, with enough practice they do eventually learn to control them. But it s an eerie question: why have their powers increased? Charlotte starts school. She s smart, ambitious, and immediately finds Lewis attractive. The only problem is he s going out with Cleo. Not for long. While learning how to control their new powers, Lewis won t leave the girls alone and smothers Cleo. She can t handle it anymore and reluctantly breaks up with him. Lewis is devastated but Charlotte quickly takes her opportunity to spend more time with Lewis. They connect. Soon, Lewis finds himself torn. Charlotte finds the moon pool and becomes a mermaid! Emma, Rikki and Cleo take Charlotte in as the fourth mermaid but it is clear this can t last. Soon all the planets line up to form the biggest full moon event in history. Finally Emma, Rikki and Cleo discover the answer to why their powers increased. And they re going to need all the help they can get.