Heigl stars as Tessa Connover, who is barely coping with the end of her marriage when her ex-husband, David (Stults), becomes happily engaged to Julia Banks (Dawson)—not only bringing Julia into the home they once shared but also into the life of their daughter, Lilly (Isabella Rice). Trying to settle into her new role as a wife and a stepmother, Julia believes she has finally met the man of her dreams, the man who can help her put her own troubled past behind her. But Tessa’s jealousy soon takes a pathological turn until she will stop at nothing to turn Julia’s dream into her ultimate nightmare.