On a shimmeringly hot Sunday in May, the Delaneys open their pool to all the village for charity. Louise is there with her daughters Amelia and Katie - and glaring at her resentfully is her estranged husband Barnaby. This is supposed to be his day with the girls - but Louise ignores his angry glowers.
While the children splash and shriek in the cool, blue waters, she lies blissfully back in the sun and dreams of Cassian, the charismatic new lawyer in her life. The day seems perfect.
But suddenly the bliss is shattered, as tragedy strikes. And the consequences of a terrible accident develop into a drama of recriminations, jealousy and legal power-play, in which Louise finds herself pulled in three directions at once. Friendships crumble, the village is split, and the needs of a child become secondary to the dangerous contest in which the grown-ups are engaged.