There's something in the water and Donald's got to look after it. On a quiet Scottish Island, local man Donald must navigate the dangerous social waters as mermaids are spotted. Unable to reject his inherent decency, Donald helps a stricken mermaid and engages the assistance of Irish incomer Kiera. When a fisherman is killed, they flee the growing rage as the locality rips itself apart in the name of revenge. With the local presbytery demanding a response, glamour models challenging the reserved image of the island and a rejected child hunting these new mammals, can Donald and Kiera keep a human fish under wraps and out of sight? Or will they succumb to the sharp end of a harpoon? Keep a good watch 'cos something's stirring the water.