Top star Momo falls into a coma after an unexpected accident. Her mother, Ran-hee, proposes a shocking solution to Momo's lover, neurosurgeon Ju-sin, to transfer Momo's soul into her own body through a brain transplant. Although it is a dangerous gamble, Ju-sin makes the fateful decision to perform the surgery.

Six months before Momo's accident, Yong-joong learns that Ba-ra is the child he met 16 years ago. Meanwhile, Ju-sin pressures Momo to marry him. Although she resists, Ju-sin sends expensive pieces of jewelry and promises to take responsibility, leaving Momo increasingly torn despite her mother's strong opposition.

Momo goes missing after a scuba diving accident. Ba-ra, a journalist, senses something suspicious about the case, while Yong-joong also feels an unsettling vibe from Ju-sin. Meanwhile, Ba-ra reveals the engagement of Ju-sin and Momo in an exclusive interview without informing him, as Momo calls 911 to report her mother's death.

Ran-hee's lifeless body is taken away, and Ju-sin mourns for Momo. The funeral proceeds, but those around her cannot believe she would take her own life with no apparent reason. Meanwhile, Momo, who now carries Ran-hee's soul, pretends to mourn while contemplating the possibilities of her new life.

Ju Shin begins to feel a growing sense of unease toward Ran Hee, who now has Momo's appearance. Over a meal with Jin Ju, Ju Shin tries to gauge her feelings. Meanwhile, Yong Joong confesses his feelings to Ba Ra, and Ba Ra begins to see hallucinations of Momo.

Ran Hee grows increasingly irritable as she tries to get closer to Ju Shin. However, Ju Shin seeks out Jin Ju, shows interest in her, and urges her to undergo the surgery. After meeting Gwang Cheol, her supposed biological father, Jin Ju vanishes without a trace, leaving behind only a single letter that shocks everyone.

Ju Shin successfully transplants Jin Ju into Momo's body. As she begins life as Momo, her biological father searches for her, waiting and refusing to believe she's dead. Meanwhile, Jin Ju offers Ba Ra a job to work by her side, and Ju Shin grows drawn to Ba Ra as he senses something is off with Jin Ju.

As Ju Shin looks deeper into Ba Ra, he finds himself increasingly drawn to her and even makes her an unthinkable offer. Ba Ra accepts Momo's proposal, quitting her job to stay by her side, while Jin Ju's father continues his relentless search for her. Meanwhile, Jin Ju, as Momo, discovers she's pregnant and hesitantly confides in Ju Shin.

Jin Ju seeks revenge on Ba Ra and tries to seduce Yong Joong while in Momo's body. Meanwhile, Gwang Cheol continues to appear before Jin Ju, who now inhabits Momo's body, pressuring her at every turn. Amid it all, Ju Shin and Ba Ra find themselves drawn into a tense, ambiguous moment as they head into the bedroom together.

As Jin Ju reels from Gwang Cheol's shocking visit, she cuts ties with Ju Shin and turns to Yong Joong, with whom she shares a past. She urges him for his full support, and they go to a karaoke room for drinks. Meanwhile, certain of his feelings, Ju Shin shocks Ba Ra with a marriage proposal.

Yong Joong warns Ba Ra to keep her distance from Ju Shin, but the two only grow closer. As Ju Shin continues to pursue Ba Ra, Jin Ju learns that Ju Shin had proposed to Ba Ra and gets overcome with fury. Suddenly, panic overcomes Ju Shin as he learns that Ba Ra is secretly planning to go away.

Yong Joong tells Ba Ra they should set a wedding date, but Ba Ra leaves him and heads to Ju Shin's house. Meanwhile, Gwang Cheol begins volunteering at Nua General Hospital, and Jin Ju is delighted when she hears something unexpected from Yong Joong.

Ba-ra is devastated to learn that Jin-ju is actually Momo and confronts her with a final plea. Despite this, Jin-ju and Yong-joong go through with their wedding. Meanwhile, Ju-shin asks Ba-ra if she would consider undergoing a brain change into Momo's body to be with Yong-joong.

Yong-joong and Ju-shin discover Ba-ra's pregnancy. After seeing Momo wearing Jin-ju's earrings, Gwang-cheol's suspicions deepen. At Paul-kim's house, Ba-ra stumbles on a picture that looks just like her. Meanwhile, Yong-joong and Momo's relationship hurtles toward an irreversible breakdown.

Cornered and desperate, Jin-ju tries to convince Ba-ra to undergo the brain swap. Meanwhile, Yong-joong promises Ba-ra eternal love, and Jin-ju begins to reveal the full truth behind the brain change to Gwang-cheol. Later, when Yong-joong visits Ba-ra at the hospital, he finds that she has disappeared.

Gwang-cheol is devastated by Jin-ju's death and, consumed by rage, confronts Ju-shin. As Yong-joong mourns Jin-ju, Paul Kim shocks James with news about his long-lost daughter. Meanwhile, Jin-ju appears at the funeral as a spirit, and a body is discovered at Nua Hospital.