“Mystery Girls” centers on two ex-stars of a detective TV series who are reunited by an actual mystery. Charlie Contour, now a suburban mom and housewife, and Holly Hamilton, who yearns for her 90s television fame, find their lives turned upside down when Nick, a crime witness and avid fan of “Mystery Girls,” insists on speaking only to them. The once-close friends must come together again and apply their on-screen detective expertise to solve a real-life case.