It could be argued that “Savage State” ultimately seems worse than it really is only because the opening scenes of this French-Canadian-produced period drama are so deceptively promising. But, really, writer-director David Perrault (“Our Heroes Died Tonight”) has no one to blame but himself. Despite any good will (or at least simple curiosity) he might generate during his intriguingly offbeat first-act set-up, he actively encourages his visually splendid but dramatically fuzzy film to gradually devolve into a gonzo mashup of gothic melodrama, Wild West survival story, and voodoo-flavored supernaturalism, with a side order of slasher-movie tropes and a sprinkling of kinky sex insinuations.

“Savage State” begins by noting that, as early as 1861, Emperor Napoleon III warned “French settlers on the new continent” to maintain “strict neutrality” during the American Civil War. But by December 1863, Edmond (Bruno Todeschini) — paterfamilias of a well-to-do French family situated in St. Charles County, Mo. — recognizes...