The coastal town of Bristol Cove, known for its legend of once being home to mermaids, is turned upside down when a mysterious young woman (Eline Powell) appears and begins wreaking havoc upon the small fishing town. Marine biologists Ben (Alex Roe) and Maddie (Fola Evans-Akingbola) work together to find out who and what drove this primal hunter of the deep sea to land, and are there more like her out there ...