Jobless, penniless, and, above all, hopeless, the unmotivated patriarch, Ki-taek, and his equally unambitious family--his supportive wife, Chung-sook; his cynical twentysomething daughter, Ki-jung, and his college-age son, Ki-woo--occupy themselves by working for peanuts in their squalid basement-level apartment. Then, by sheer luck, a lucrative business proposition will pave the way for an insidiously subtle scheme, as Ki-woo summons up the courage to pose as an English tutor for the teenage daughter of the affluent Park family. Now, the stage seems set for an unceasing winner-take-all class war. How does one get rid of a parasite?

Sok-woo and his daughter Soo-ahn are boarding the KTX, a fast train that shall bring them from Seoul to Busan. But during their journey, the train is overrun by zombies which kill several of the train staff and other passengers.While the KTX is shooting towards Busan, the passengers have to fight for their lives against the zombies.