In her mid-40s, burnt out and seeking sanctuary, Frankie Rowley walks away from life as an aid worker in Africa and returns to the lush, perpetual late summer of the New England world in which her parents are drifting into tranquil senescence. But there is trouble in paradise: on Frankie's first night back a nearby summerhouse goes up in flames, swiftly followed by more, and the community suspects the presence of an arsonist in their midst who threatens the charmed existence of the "summer people".

The Arsonist explores similar themes to Miller's last novel, The Senator's Wife: marriage, family and the modulation of relationships over time, about which Miller writes with penetrating honesty. As Frankie's father, Alfie, a promising but never brilliant academic, succumbs to dementia, her mother, Sylvia, reflects on their life together and its mismatch with her youthful expectations. More than Frankie's return – more even than the disruptive presence of the arsonist – it is the slow atrophy of Alfie's intellect, and the responses it elicits from those around him, which lies at the heart of the novel, and which Miller handles with a deft, homespun acuity.