A zombie virus breaks out in Busan and spread across the rest of the country. Seungbeom turns into a zombie, but, with the help of his girlfriend Jiyoon, gets vaccinated and returns to normal. A year after the vaccine comes to the rescue, those previously afflicted with the virus are still subject to invisible discrimination. Having survived the zombie virus that lasted for four years, Seungbeom proposes to Jiyoon, and she reveals a secret that she’s been withholding from him.