Donald believes he knows all there is to know about seeing. An optometrist in suburban Boston, he is sure that he and his wife, Viv, who runs the local stables, are devoted to their two children and to each other. Then Mercury—a gorgeous young thoroughbred with a murky past—arrives at Windy Hill and everything changes. Everyone at the stables is struck by Mercury's beauty and prowess, particularly Viv. As she rides him, she begins to dream of competing again, embracing the ambitions that she had harbored, and relinquished, as a young woman. Her daydreams soon morph into consuming desire, and her infatuation with the thoroughbred escalates to obsession. Donald may have 20/20 vision but he is slow to notice how profoundly Viv has changed. By the time he does, it is too late to stop the catastrophic collision of Viv's ambitions and his own myopia.