Set at the start of the 17th century, three years after the end of the Imjin War, Kingdom takes place in a fictional, medieval-inspired Joseon (modern-day Korea) and blends political thriller and elements from zombie horror. The story follows Lee Chang, the Crown Prince of Joseon, who attempts to investigate the mysterious illness recently afflicting the King, only to find himself caught in the middle of a deadly epidemic ravaging the kingdom. While trying to save the Kingdom from the plague, he must also stop his political opponents from seizing the throne.