Lily Ross has murdered her mother. Her lover, Martha, searches for the motive. In her prison cell Lily reflects on a past and future, both real and imagined - a mother and grandmother living off dreams and alcohol, an academic father enclosed in his world of butterflies, and Teddy, the older man she seduced on the beach when she was just fourteen. Gradually, as through a glass darkly, we begin to perceive the complex web of events which leads Lily inexorably to her extreme act.