Doc filmmaker Liz Garbus' narrative feature debut “Lost Girls” is based on the famously unsolved Long Island serial murders. Amy Ryan stars as a mother driven by police inaction to investigate her daughter's disappearance in an unsatisfying Netflix movie that punishingly goes through the motions of the procedural genre. If anything, last year’s Netflix true-crime police procedural “Unbelievable” tackled similar territory but in far more shattering and forensically-detailed fashion. The Long Island Serial Killer case, from the late ‘80s, involved the murders of more than a dozen sex workers over a period of almost 20 years, but the poorly scripted “Lost Girls” is so uninvolving that it manages to make the real-life tragedy an incredibly dull affair. Ryan plays enraged mom Mari Gilbert, trying to trace back the steps of her missing daughter Shannan, while having to deal with her two other teenage daughters at home, Sherre (Thomasin McKenzie) and Sarra (Oona Laurence). To make matters worse, a frustratingly unsympathetic detective (Dean Winters) doesn’t seem to be in any rush to solve the case, ditto the clumsy police commissioner (Gabriel Byrne) sleepwalking through the developments. So Mari, like any good mother in these kinds of movies, starts posting fliers and banging on doors, this rings the alarm of a few locals who might have a connection to the unsolved cases and riles local police. Written by Michael Werwie (“Extremely Wicked, Shockingly Evil and Vile”) and inspired by journalist Robert Kolker's book, “Lost Girls: An Unsolved American Mystery,” Garbus’ film would have been better served as a documentary as she struggles to find coherence in the story she is trying to tell on-screen. Clocking in at a tepid 95 minutes, “Lost Girls” feels incomplete, not developed enough for us to be immersed into the story, the result is a suspense-free procedural with barely any stakes at hand. [D]