The screenplay is based on the novel Journey (Korean: 원행; RR: wonhaeng; lit. "a round trip") written in 2006 by Oh Se-yeong. The background of the action is the 1795 procession organized by King Jeongjo of Joseon for the 60th birthday of his mother, Lady Hyegyeong that also commemorated the 60th birthday of his deceased father, the Crown Prince Sado. During the eight days period when the Court left the palace for the ceremony, the show introduces several assassination attempts against the King. A first one comes from the Moon In-bang's group (a millenarist sect). But this plot is used by the Noron Faction to pursue its own agenda, attempting an armed suppression against the Sipa Faction and the King as well.
Apart from the fictional elements, a major focus is placed on two historical sources. The Memoirs of Lady Hyegyeong is extensively used during many flashback sequences relative to events that occurred before the death (1762) of Crown Prince Sado, while the official documents from the Joseon Royal Library are used for the current events: the "Wonhaeng Eulmyo Jeongni Uigwe" (Eulmyo=1795) for the procession itself, and the "Hwaseong Seongyeokuigwe" concerning the Hwaseong Fortress as a whole.
This series is often referred as Eight Days, Mystery of Jeong Jo Assassination, a misleading translation since King Jeongjo won the 1795 confrontation and only died in 1800.
