Horror movies can serve many metaphorical purposes, but it’s still kind of startling to watch Yeon Sang-ho’s zombie tale become a potent exploration for what it actually means to preserve one’s humanity. There’s nothing particularly promising in the set-up, which finds fund manager Seuh Seok-woo (Yoo Gong)—yes, he’s a workaholic dad who needs to learn What Really Matters—escorting his young daughter (Su-an Kim) back to his ex-wife’s house on the train, just as a chemical accident is turning South Korea into a zombie apocalypse. Yeon underline’s Seok-woo’s dickishness a bit too bluntly early on, but the complaints start to dissolve once the story turns into a contained-space thriller that builds some terrific set pieces around characters trying to make it through pockets of undead to the “safe” cars. But it’s even better at watching as fear turns the survivors into a different kind of animal, suspicious of any new arrival among them. Along with its ample genre satisfactions, it asks alarmingly timely questions about what we’re teaching our children about abandoning compassion for a fleeting sense of security.