Season 1

After getting alarming news from his fiancee, Cha Min has a mishap and receives an object called Abyss; Go Se-yeon meets someone who says that he is a friend.

Min explains what he did to Se-yeon, who is in disbelief over her circumstances; vowing to find her killer, she comes up with a way to help Min and herself.

Se-yeon and Min are stunned by what Park Gi-man has been doing, and they unwittingly get help from a police detective who thinks that she is someone else.

Convinced that he has seen his ex-fiancee, Min is frantic to talk to her, but Se-yeon tries to remind him that he is not the same person anymore.

After making a horrific discovery, Se-yeon considers using Abyss and tries to persuade Park Dong-cheol to keep investigating the murder of the prosecutor.

Park Dong-cheol tries to hunt down Oh Yeong-cheol, who keeps eluding the police; Min's mother doesn't know what to make of the changes she sees in her son.

Se-yeon finds herself viewing Min in a different light after realizing he has always been by her side; Jang Hui-jin reveals something surprising to Min.

Park Dong-cheol demands to know why Se-yeon interferes with the case; someone claiming to be Lee Mi-do appears out of nowhere.

Se-yeon tries to explain her actions to Min and has an emotional reunion with her mother; Hui-jin refuses to back down upon being confronted by Min's mother.

Se-yeon gets a feeling that she may be in danger, Min reveals a secret about his father, and Hui-jin's mother becomes agitated after seeing someone on the television.

After Park Dong-cheol alerts him about Oh Yeong-cheol, Min goes looking for Se-yeon. Lee Mi-do's parents get a perplexing proposal from Min's mother.

Se-yeon senses something unnerving about Seo Ji-uk; Hui-jin gets an unexpected visitor and has an idea about what Oh Yeong-cheol could be planning to do.

While attempting to help Park Gi-man with a case, Se-yeon and Min discover something strange; Seo Ji-uk gets a visitor.

Seo Ji-uk puts his plan in motion. On the way to meet Se-yeon, Min receives a disturbing call from Park Dong-cheol and struggles with a difficult decision.

Min and Se-yeon set out to acquire evidence against Seo Ji-uk, with Park Dong-cheol's help; Min's mother questions Se-yeon about her intentions.

After proposing to Min, Se-yeon copes with the consequences of his sacrifice and reveals the truth to her parents; Seo Ji-uk's trial begins.