On a blustery April day, the wife of a doctor discovers that her husband has been having an affair. Moments later, driving along a country road, she fails to see sixty-one-year-old Ruth Mitchell up ahead, riding her bicycle. She hits her, killing her instantly, and drives away. Horrified by what she has done, she turns her attention to Ruth's bereaved husband, a man as unhinged by grief as she herself is by guilt. And as she insinuates herself into his life, he starts to believe that, for reasons beyond his understanding, his wife has returned to him.