Perfect families, perfect houses, perfect lives.

Three mothers, Jane, Madeline and Celeste appear to have it all, until they find out just how easy it is for one little lie to spiral out of control . . .

Single mum Jane has just moved to town. She's got her little boy in tow - plus a secret she's been carrying for five years.

On the first day of the school run she meets Madeline - a force to be reckoned with, who remembers everything and forgives no one - and Celeste, the kind of beautiful woman who makes the world stop and stare, but is inexplicably ill at ease.

They both take Jane under their wing - while careful to keep their own secrets under wraps.

But a minor incident involving the children of all three women rapidly escalates: playground whispers become spiteful rumours until no one can tell the truth from the lies . . .

It was always going to end in tears, but how did it end in murder?

London, 1893. When Cora Seaborne's controlling husband dies, she steps into her new life as a widow with as much relief as sadness. Along with her son Francis - a curious, obsessive boy - she leaves town for Essex, in the hope that fresh air and open space will provide refuge. On arrival, they hear rumours that the mythical Essex Serpent, once said to roam the marshes claiming lives, has returned to the coastal parish of Aldwinter. Cora, a keen amateur naturalist, is enthralled, convinced that what the locals think is a magical beast may be a yet-undiscovered species. As she sets out on its trail, she is introduced to William Ransome, Aldwinter's vicar, who is also deeply suspicious of the rumours, but thinks they are a distraction from true faith. As he tries to calm his parishioners, Will and Cora strike up an intense relationship, and although they agree on absolutely nothing, they find themselves at once drawn together and torn apart, affecting each other in ways that surprise them both.