Lilly Rush is the only female detective on the Philadelphia Homicide Squad, working with the Cold Case unit, investigating unsolved, often older, murders. She has a habit that some of her colleagues and friends find a little strange - while investigating a case, she keeps a photo of the victim(s) by her bedside.Like most police, particularly female police, in television programs, Lilly has some problems finding a steady love interest in her life. She also has unresolved family issues that re-appear from time to time.