Starting an affair with Robert is easy. Bored with the awkward, boorish single men of her own age and flattered by the confident attentions of a handsome stranger, Harriet is excited by the idea of a lustful friendship, as Robert chooses to describe it. A commitment-free fling is ideal, and the existence of a wife is a minor inconvenience. But then Harriet finds out about his other mistress ... So, escaping the heat and hubbub of a musician's life in London, for the sleepy seclusion of a cottage on a farm in Somerset, Harriet begins to plan exactly how she is going to eliminate her enemy.