Despite vowing to be friends for ever, life inevitably gets in the way. So in a holiday cottage by the beach, four women decide that they need to reconnect. Each will write an anonymous letter sharing their deepest secrets. Everything from marriage problems to financial woes, from secret addictions to forbidden crushes. And each new discovery draws them closer together. But there's a fifth letter. One that shouldn't exist. A letter that reveals one woman's secret obsession with another. An obsession that is turning to hatred. And there is no way of telling which one of them is now in danger . . .