Lee Gon mourns the tragic death of his father. Lee Lim goes on the run — and finds escape when he comes across a door to a parallel universe.

Gon insists he is an emperor from another world. An incredulous Jeong Tae-eul takes him to the police station, where he sees a familiar face.

Though Tae-eul finds Gon's story difficult to believe, some things about him are completely inexplicable. At work, she gets busy with a murder case.

When Tae-eul loses her police badge, she can't help but think about Gon. Meanwhile, Kang Sin-jae has had it with his mother's bad habits.

Being introduced to Gon's world is a lot to process for Tae-eul, who's taken to the palace. A disgruntled Jo Yeong keeps an eye on her.

A potential military conflict threatens the kingdom. Gon promises Tae-eul he will return to her, and steps forward to take care of the situation.

Gon brings Yeong along on his trip back to Tae-eul. He has a favor to ask of her, while she's found something troubling to share with him.

In Corea, Luna is set free. In Korea, Gon and Yeong run into a man who recognizes them, and Sin-jae experiences childhood flashbacks.

Gon draws closer to tracking down Lim, and asks Jo Eun-sup to trade places with Yeong. Mail from an unknown sender bothers Koo Seo-ryeong.

On Lunar New Year, Gon and Lim come face-to-face in a public standoff. Tae-eul opens up to Sin-jae about the other world and her ongoing case.

A compelling offer finds its way to Luna. Gon's investigation into a devastating murder leads him to an old traitor and a clearer idea of Lim's schemes.

Frightening circumstances land Tae-eul back in Gon's arms. When Yeong runs into a woman who looks strikingly familiar, he follows her.

Knowing Seo-ryeong is up to no good, Gon throws her in a tight spot. Upon returning to her world, Tae-eul realizes Luna is there, too.

Lim plots his next meeting with Gon. Understanding there's only one thing he can do to right wrongs, Gon comes to a heart-wrenching decision.

A final attempt to put a stop to Lim's ambitions comes with profound consequences. Gon travels far and wide in search of Tae-eul.