After he’s attacked on the street by a roving motorcycle gang, timid bookkeeper Casey joins a karate studio to learn how to protect himself. Under the watchful eye of a charismatic instructor, Sensei, and brown belt Anna, Casey gains a newfound sense of confidence for the first time in his life. But when he attends the mysterious night classes, he discovers a sinister world of fraternity, brutality and hyper-masculinity, presenting a journey that places him squarely in the sights of his enigmatic new mentor.