On a blustery April day, the quiet, rather private wife of a doctor discovers that her husband has been having an affair. Moments later, driving along a winding country road and distracted perhaps by her own thoughts, perhaps blinded by sunlight, she fails to see sixty-one-year-old Ruth Mitchell up ahead, riding her bicycle. She hits her, killing her instantly. And drives away. The hit-and-run driver is never found. But the doctor’s wife, horrified by what she has done, begins to unravel. Soon she turns her attention to Ruth’s bereaved husband, a man staggering sleeplessly through each night, as unhinged by grief as the killer is by guilt.