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.

Simple-minded Joseph Briteman breaks a golden rule of his 'life skills' program when he walks away unsupervised to rescue his long lost baby sister.