Gen Ziegler left her home in tiny Mount Ebal, Pennsylvania right after college, to get as far away from her mirror-image twin, Sara, and their dysfunctional relationship as possible. Now, five years later, Dr. Ziegler teaches at the University of Arizona and assists the Tucson Police as a forensic psychologist. Yet, all her life Gen's had clairvoyant flashes, telling her when Sara was in danger. One new vision is so vivid, Gen flies home to find that her sister is the primary witness and suspect in a grisly stabbing death. The last person Sara wants around is Gen, but if the real killer isn't found, one or both sisters will become victims themselves.