Gone Girl author Gillian Flynn’s other bestseller becomes a movie courtesy of writer-director Gilles Paquet-Brenner, a French filmmaker with a penchant for solemn survivor-guilt stories of child endangerment. Whereas his previous film Sarah’s Key was a true Holocaust tale, Dark Places is a fictional contemporary mystery, its young siblings subjected to murderous fury not from Nazis, but from…well, that’s the mystery. Libby and Ben — played by Sterling Jerins and Tye Sheridan as youngsters and by Charlize Theron and Corey Stoll as adults — escaped the killing of their entire rural Kansas family in the mid-1980s, she by jumping out a window, he by apparently having been the perpetrator. But that version of events doesn’t sit right with a handful of true-crime groupies who track the adult Libby down and convince her to visit Ben in prison. Like a long, less fun episode of Dexter — with its sheen of cheese, its flat expository narration, its belabored insistence on “darkness” — the picture is dim twice over: under-lit and unclever. Its talented cast also includes Nicholas Hoult, Christina Hendricks, and Chloë Grace Moretz, but the plodding material doesn’t manage to serve any of them particularly well. Cross-cutting between past and present seems trudging and obligatory, illustrating the difference between suspenseful and just plain stretched out. Flynn fans probably will be divided on how well this enterprise honors her book. With regard to its merits as a movie, well, for a guy who apparently likes digging into intense memories, Paquet-Brenner has an unfortunate habit of dramatic forgettability.