Lee Soo Hyun (Ji Jin Hee) can't seem to escape a haunting reoccurring dream about a woman from 1,000 years ago, so as the CEO of a gaming company, he uses that dream as the basis for an online game he calls "Lucid Dream." When Han Yun Hee (Lee Ji Ah), a part-time employee on leave from art school, reads the game’s script, she becomes unsettled as it coincides with her own dreams of a life filled with tumultuous romance. She finds she has an unexplainable connection to the game creator, but he is already engaged to a woman (Seo Ji Hye) desperate to keep them apart, and she is held back by another former flame (Ahn Jae Hyun), who continues to haunt her reality.