Demons aren’t the only howlers in this supernatural thriller inspired by the Hellblazer comic books. As the title character, a failed suicide who tracks errant devils to return them to the underworld, Keanu Reeves gets all the good lines, and he hits the right ironic notes for a neo-noir gumshoe who’s also an exorcist. But the rest of the cast—including Rachel Weisz, Tilda Swinton, and Djimon Hounsou—is stuck with the heavy lifting, trying to inject a modicum of credibility into the fevered nonsense about a spear of destiny that will call forth Satan’s son. Philippe Rousselot’s elegant cinematography lends some gravitas to music-video veteran Francis Lawrence’s directorial debut. R, 121 min.