On the night of the full moon, Zac and Erik swim to Mako Island and unlock the merman chamber, revealing a startling secret.
When a young mermaid follows Ondina back to Mako Island after a mermaid council meeting, it could spell trouble with the pod.
When the pod decides Zac is a threat and must give up his merman powers, two new mermaids, Mimmi and Ondina, are sent to make sure he obeys.
