The Hotel del Luna (formally referred to as the “Guest House of the Moon”), located in Myeong-Dong, Seoul, is not like any other hotel: its clients are all ghosts, and it is not visible in its true form during the day. Humans can only come across the hotel under special circumstances, for example, during a Lunar eclipse.
During the Goguryeo era, a rebel named Jang Man-wol (IU) went through a series of tumultuous events that led to her committing several sins. She escaped from her captors and began her search for the “Guest House of the Moon” as she felt that she had wronged those who died because of her and held a strong grudge. She drank a liquor made with “Moon flowers” offered to her by a deity (Mago) that unknowingly turned her into the guest house’s owner while she was traveling to find it. She has been stuck to the “Moon Tree” ever since and has been running the hotel for more than a 1,000 years before meeting Koo Chan-Sung (Yeo Jin-goo), the new manager. Koo Chan-Sung was deemed to be just the right person for the job by Mago as Mago believes that he holds the key to the freedom of Jang Man-Wol from the guest house.
The 16 episodes of the series depict how Koo Chan-Sung adjusts to his new ability to see ghosts, his new job, and the tantrums of his fickle new employer. The hotel has several staff members, the oldest being the bartender Kim Seon-Bi, the head wait-staff Choi So-Hee, and the doorman Ji Hyeon-Jung. Over time Koo Chan-Sung wins the hearts of all the members working in the hotel and together they serve their guests by trying their best to give them a satisfactory experience before they leave for the afterlife.
The “Moon Tree” that had seemed to be dead for a thousand years sprouts leaves and blossoms as the bond between Koo Chan-Sung and Jang Man-Wol deepens and they begin to date. The leaves and flowers begin to shed once Jang Man-Wol realises the problems and risks her hotel’s manager has to face because of her and she begins to fear for his life.
Jang Man-Wol comes across several people she was acquainted with in the past which brings up bitter memories. But with the help of Koo Chan-Sung and her hotel staff, she overcomes them and moves on. Jang Man-Wol leaves the hotel to drop-off a person from her past to the bridge to the afterlife.
The days roll by and soon enough the branches of the “Moon Tree” are bare. Jang Man-Wol returns to the hotel after a month much to Koo Chan-Sung’s happiness. The hotel staff and the guests leave one by one as they have each gotten their closure and because the time for Jang Man-Wol to leave the hotel forever has arrived.
Jang Man-Wol and Koo Chan-Sung share an emotional farewell as Man-Wol leaves for the afterlife alone after they both promise to meet each other in the next life. After she leaves, the hotel closes down as well.
Time goes by and Koo Chan-Sung tries to move on. He goes abroad while hoping for the best. Meanwhile, Mago has found a new owner for the “Guest House of the Moon”, a man who names the place “Hotel Blue Moon”. The series ends with a sense of mystery.