Cannibals in Viking gear are the unlikely, but at least original, villains of "Tooth and Nail," a well-acted, professionally lensed post-apocalyptic thriller that was reportedly shot in only twenty days. When the majority of the population dies off after the world runs out of gas, a group of survivors seek shelter at an abandoned hospital. After they bring another young woman named Neon (Rachel Miner) into their fold, following not far behind are Rovers, a band of savage mercenaries who want to make the lot of them their next week's worth of food. Written and directed by Mark Young, "Tooth and Nail" dawdles at the onset and takes some time to get going. Once it does, the film packs a hard-core violent punch that leads toward a twist that is genuinely surprising. What follows this is pretty riveting stuff, and not even an out-of-place turn from Michael Madsen as one of the Rovers can destroy the picture's strengths.