Half sisters Flora, Kat, and Lauren spent every August with their shared father at his seaside Cornwall estate. That is, until an unspeakable tragedy ended their carefree summer tradition. Twenty years later, the three women lead very different lives, but they agree to reunite at their father's behest to say goodbye to the memories buried there. However, someone is watching them, someone who won't let them forget that fateful summer… and the family's darkest secrets are about to come to light.