Dale copes with the fallout from Maddie and Ryn's encounter with the man from Susan's past, while Katrina continues to persuade the rest of the mermaid pack to get on her side, even if that means brute force against both mermaids and humans.
The coastal town of Bristol Cove is known for its legend of once being home to mermaids. When the arrival of a mysterious girl proves this folklore all too true, the battle between man and sea takes a very vicious turn as these predatory beings return to reclaim their right to the ocean.