Cha Do Hyun es un chico que sufre de trastorno de personalidad múltiple, en una noche de discoteca conoce a la psiquiatra Oh Ri Jin, de quien termina enamorado. Su hermano gemelo Oh Ri On es un famoso escritor conocido como Omega.

Oh Ri Jin cura a Cha Do Hyun después de la pelea que tuvo fuera del antro. Seok Ho-pil es atacado por la otra personalidad de Do Hyun quien desea controlar su mente, esta vez por un motivo muy grande.

Cha Do Hyun necesita que Shin Se Gi salga, pero al ser golpeado por su asistente termina despertando a Perry Park, poniendo en riesgo a la psiquiatra Oh Ri Jin. Después de ser rescata la psiquiatra se entera de las personalidades de Do Hyun.

Cha Ki-joon quiere investigar sobre Cha do Hyun. Después de conocerse más la doctora y Do Hyun, él desparece. Han Chae se muestra celosa al enterarse que Cha do Hyun está interesado en otra mujer. Shin Se Gi va en busca de la doctora.

Shin Se Gi secuestra a la doctora y la lleva a un hotel y le exige que elija entre él y Cha Do Hyun. Shin. Seo Tae-im le advierte a la madre de Do Hyun, que, si continúa con sus impertinencias, el único perjudicado será su hijo.

On Ri Oh encuentra a su hermana y a Do Hyun en una situación comprometedora, por otro lado, Do Hyun sigue luchando con sus personalidades. Oh Ri Jin renuncia a ser la psiquiatra de Cha Do Hyun, y lo llama para despedirse.

After getting through a life-threatening situation with Ahn Yoseop, Rijin is left with the decision to either leave for America or become Dohyeon's doctor. Cha Gijoon tries to look into why his cousin sees a psychiatrist.

Rijin discovers a new personality in Dohyeon when he learns about one of Omega's stories. Han Chaeyeon begins to feel jealous that Dohyeon might like Rijin.

Rijin encounters virtually all of Dohyeon's personalities in one night. Dohyeon makes a shocking revelation when he finally finds out who Writer Omega truly is.

Segi grows angry when he discovers that Rijin has been spending time with Dohyeon. Rijin grows worried when she's told that Dohyeon may never return to recover his forgotten memories.

Rijin encourages Segi to share the painful childhood memory with Dohyeon, and discovers what Oh Rion has been hiding in his room.

Dohyeon finally recovers a crucial piece of his forgotten memories and is now determined to become stronger and bear the burden. Chaeyeon is conflicted about her upcoming engagement to Gijoon.

Dohyeon vows to find the other mysterious child that was also at the Seungjin mansion when he was a boy. Rion is caught off-guard when the teenage girl personality, Ahn Yona, suddenly appears.

Rijin discovers that her own childhood memories are emerging in the pursuit to recover Dohyeon's memories. Dohyeon finds out the truth of what happened in that basement during his childhood days.

Rattled by the truth of the memories he shares with Rijin, Dohyeon is committed to living the rest of his life in repentance. Rion asks Dohyeon to step in so that Rijin doesn't recall her childhood memories.

Dohyeon and Rijin embark on a trip together before their contract is terminated. As Rijin starts to recall more of her past, the memories bring with it deeply buried pains, and most importantly, the truth.

More memories of the past come to light for Dohyeon and Rijin. Dohyeon confronts his grandmother about the fire that took place twenty-one years ago and learns who truly started the fire.

Dohyeon's personalities appear over the course of one night when he learns the entire truth. However, a past threat appears to break his resolve once more.

Rijin and Dohyeon embark on their cathartic journey to deal with their shared painful memories. But just as they begin, another personality shows up to threaten their progress.

Dohyeon bids farewell to all of his personalities with the help of a new personality, and finally confronts his family about the past.