Rosemary Fielding is delighted when impresario and family friend Oliver Duncan suggests turning her novel into a mini-series. However she's less kindly disposed towards his choice of leading man, the actor Stephen Walker, and dreads having to meet him. True to his reputation, Stephen is rude and arrogant causing Rosemary to retaliate. With Oliver insisting they settle their differences, author and actor spend a weekend together. Rosemary introduces Stephen to the delights of the Norfolk countryside and likens their blossoming relationship to the scarlet and black cinnabar moths that abound. But the colours of the cinnabar also herald danger. Increasingly concerned by a predator close to home, are the couple destined to share only one summer together?