Time after time, it's an idea whose validity only solidifies further, that in a creative context, lesser means often necessitate greater innovation. Within the context of the zombie horror sub-genre, it's that innovation that too frequently engenders naff, insubstantial riffs on the same trite concepts. Yeon Sang Ho, rather than lessening his means, limits his physical scope in Train to Busan, itself an attractive proposition - too rarely do high-concept thrillers like this betray their essential limitations, and suffer as a direct result. But that's not even this film's strongest asset. That comes in Yeon's interpretation of innovation, a sound and sincere calibration of character development and of mise-en-scene. The score is clunky, the cinematography is unremarkable, the dialogue is passable; it's not the individual components that raise Train to Busan above the standard of its manifold genre brethren, it's how Yeon chooses to employ them within the design of his overall scheme. He forges tension through emotion as much as through thriller fundamentals like space and sound; he crafts memorable images without sacrificing their vital narrative value, indeed crafting them from that very value; he establishes familiar plot lines before upending them in surprising, often affecting ways (his initial adherence to them, however, does cast some of Train to Busan's politics in an unflattering light). And with a focus on the human element that extends far beyond a mere depiction of heroism and vague social responsibility, Yeon's film bites harder than you ever expect it to, not least with the aid of tremendous performances from the cast. Though its excellence in many regards may be stymied by its timidity and regressiveness in others, this is a genuine display of innovation in the most satisfying manner.