Ep 21. Red Herring

Emma's annoying little brother, Elliot, discovers the moon pool and becomes smitten with Rikki. After he decides to follow them to Mako Island, he's convinced that they're hiding something from him and gets Lewis to help him investigate. Meanwhile, Ash tries to get Emma's attention, but she's too caught up in trying to keep Elliot out of trouble to notice. When one of their science experiments goes wrong, Elliot stumbles upon a clue that could unravel their secret. Will he figure it out before it's too late?