Welcome to Serenity Falls - the most idyllic, and safest, town in the US - a place to grow up, grow your family and grow old together. For Dan and his daughter, Sadie, it's the perfect relocation option. A fresh start, thousands of miles from their troubled past in the UK. But their idyll is shattered when they find a dead body in the swimming pool of their new house - a house Dan's late mother kept secret from him all his life. It's just the start of a series of disturbing discoveries. Abandoned houses where people have seemingly just upped and left. The strange woman Sadie sees around town putting up 'missing' posters for a child who drowned almost 30 years ago. An ice cream van that drives around at night making sure residents are asleep. As plans gear up to celebrate Serenity Falls' 50th anniversary, something is stirring beneath the surface of the blissful façade.