Danny Boyle’s post-modern update of George Romero’s “Night of the Living Dead” is more chilling than scary, but it’s still a pretty effective apocalyptic nightmare—even though it never quite becomes the nightmare you want it to be. The film is filled with disturbing images of a devastated Britain that stay with you long after it’s over. (A long shot of the town of Manchester seen going up in flames is particularly haunting.) Boyle has shot the film in digital video (the camerawork is by Anthony Dod Mantle) and it’s a good choice, bringing a grainy immediacy to the narrative and allowing Boyle to indulge in some flashy but useful shock editing whenever zombies infected by a “rage” virus are onscreen. But the director and his screenwriter, Alex Garland, aren’t content to let the concept of a country (and, presumably, a world) destroyed by infection be what the film is ultimately about and the second half changes direction, introducing a plot of lesser value about a crazed army major (well-played by Christopher Eccleston) whose goals for the future of mankind are intended to be as outrageous as the more gruesome elements of the story but are not, unfortunately, nearly as interesting. Still, much like “Trainspotting”, Boyle brings his indefatigable energy to the proceedings and the intensity never flags even when the ideas get shuffled around. The young, eager-to-please cast includes Cillian Murphy, Naomie Harris and Megan Burns and they’re up to a difficult task.