Kingdom: Ashin of the North, a new episode of the Korean drama Kingdom, will be released on July 23.

The special episode is referred to as a “sidequel” to the first two seasons of Kingdom, which were released in 2019 and 2020. The historical drama is set during Korea’s Joseon dynasty (1392-1897).

Kingdom: Ashin of the North will tell the story of the resurrection plant that caused people to become zombies. The 92-minute episode will star Jun Ji-hyun as Ashin, the person closest to the plant’s secret. Park Byung-eun will also appear in the episode, which is directed by Kim Seong-hyun and written by Kim Eun-hee. 

Writer Kim Eun-hee originally conceived of the story in 2011, but she thought it might be difficult to produce, so she turned it into a web comic series. The story was inspired by the Annals of the Joseon Dynasty, which recorded Korean state affairs from 1413 to 1865, and described thousands of people dying from a mysterious illness. Kim, who also wrote the hit dramas Signal and Phantom, decided to reinvent the plague as a zombie virus. 

Kingdom was the first Korean original drama series produced by Netflix NFLX . The original story revolves around a crown prince, Lee Chang, played by Ju Ji-hoon. Lee Chang must fight against the mysterious plague turning his people into zombies and also the corrupt government officials who are hungry for power and will use the plague to further their own goals. The ongoing drama also stars Bae Doo-na, Kim Sang-ho, Kim Sung-kyu and Heo Jun-ho.

The special episode will be Jun’s first TV role in four years, since she appeared in Legend of the Blue Sea with Lee Min Ho. Jun also appeared in the drama My Love From The Star with Kim Soo-hyun and the films The Thieves, Berlin File and Assassination. Jun is set to star in the Netflix drama Jirisan aka Mount Jiri, with Kingdom co-star Ju Ji-hoon.