It's the dawn of the 1930s and the three privileged Guinness sisters, Aileen, Maureen and Oonagh, settle into becoming wives and mothers: Aileen in Luttrellstown Castle outside Dublin, Maureen in Clandeboye in Northern Ireland, and Oonagh in Rutland Place in London. But while Britain becomes increasingly politically polarised, Aileen, Maureen and Oonagh discover conflict within their own marriages. Oonagh's dream of romantic love is countered by her husband's lies; the intense nature of Maureen's marriage means passion, but also rows; while Aileen begins to discover that, for her, being married offers far less than she had expected.

Meanwhile, Kathleen, a housemaid from their childhood home in Glenmaroon, travels between the three sisters, helping, listening, watching - even as her own life brings her into conflict with the clash between fascism and communism. As affairs are uncovered and secrets exposed, the three women begin to realise that their gilded upbringing could not have prepared them for the realities of married life, nor for the scandals that seem to follow them around.