Ellen Gulden is a successful, young New York journalist. But when her mother, Kate, is diagnosed with cancer, she leaves her life in the city to return home and care for her. In the short time they have left, the relationship between mother and daughter - tender, awkward and revealing - deepens, and Ellen is forced to confront painful truths about her adored father.

But in the weeks that follow Kate's death, events take a shocking and unexpected turn. Family emotions are laid bare as a new drama is played out, and overnight Ellen goes from devoted daughter to prime suspect, accused of the mercy killing of her 'one true thing'.

One True Thingis the devastating story of a mother and daughter, of love and loss, and of shattering choices.