A reckless flight attendant with an alcoholism problem wakes up in the wrong hotel, in the wrong bed, with a dead man - and no idea what happened. Unable to piece the night together, she begins to wonder if she could be the killer.

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.