The Smile Has Left Your Eyes - Season 1 (2018)

Jin Gook strongly believes that Moo Young is related to the murder of Jeong Mi Yeon and warns Moo Young that he will catch the killer no matter what. Moo Young wishes him good luck but insists that Jin Gook gets it all wrong and he isn't the killer. Never-theless, Jin Gook visits Lim Yu Ri, the witness, and asks her how the two were related. Meanwhile, Seung Ah is grounded for sleeping with Moo Young, and she asks Jin Kang a favor.

Jin Gook saves Jin Kang from an accident just in time. He goes to the driver's seat to check who the driver is and finds Lim Yu Ri, lying unconscious. They take her to the hospital, and the doctor tells them that she is just a little malnourished and has taken several sleeping pills. Jin Gook calls Moo Young over and asks him whether he told Yu Ri to intentionally hurt Jin Kang.

Jin Gook desperately tries to save Yu Ri after she tries to throw herself off the building. The burn scar that Jin Gook finds on Moo Young throws him in a state of confusion. Meanwhile, Jin Kang approaches Moo Young and demands him to clear up the misunderstanding he's caused Seung Ah, but Moo Young hints otherwise.

Jin Kang visits Moo Young's place only to witness him getting beaten up by a bunch of thugs. Alarmed and shocked, she calls the police before running to his rescue. Moo Young is taken to the hospital but ignores the doctor's advice and goes home. Jin Kang begs him to file a suit, but he tells her that the men were only paid to get the job done and that they are not at fault.

News of Seung Ah and Woo Sang's car accident are all over the place. But no record of Moo Young being admitted to the same hospital or any mention of him can be found on the news. His disappearance leaves Jin Gook and Jin Kang perplexed. Meanwhile, more evidence that point to Moo Young being the likely culprit surfaces, and Cho Rong discovers that Jin Gook had been staying silent despite knowing everything.

Evidence on Jeong Mi Yeon's murder gets found from Moo Young's house. The secret behind the incident gets revealed. After knowing what happened, Jin Gook tells Jin Kang that Moo Young is nothing more or less than an evil mastermind. However, Jin Kang finds herself still being attracted to Moo Young.

Moo Young and Jin Kang go on their first date, hand clasped and their faces beaming with smiles. But Jin Kang keeps her relationship a secret from Jin Gook. Moo Young decides to be the good guy Jin Kang wants him to be. Meanwhile, Jin Gook opens up about something from his past to So Jung, which leaves her in shock.

Jin Gook finds out Jin Kang went to Haesan with Moo Young and gets furious about it. Jin Gook gets more and more anxious about the inseparable two. Leaving her worried brother behind, Jin Kang fills in Moo Young's house with appliances and gets ready for a housewarming party.

Jin Gook tells Jin Kang that he stabbed Moo Young which shocks her. Jin Gook says he can do even worse things if it will separate the two. Without fully knowing why, Jin Kang promises that she will never see Moo Young again. When she meets Moo Young, she realizes that it is irresistible.

Moo Young goes to Haesan again to see where his father supposedly committed suicide. At his old house he finds, some parts of his memories come back to him and he realizes something shocking. Back to Seoul, he goes to Se Ran to ask a favor.

Moo Young goes to Jin Gook with a gun, who was expecting him to come. Later, Moo Young goes to Se Ran and finds the truth behind the incident related to his father. The truth only devastates him even more. Jin Kang is the only one who can comfort him.

Moo Young tells Jin Kang that he doesn't want to see her anymore. Jin Kang asks him why, but he can't tell her the reason. Desperately looking for answers, she goes to So Jung to at least understand why Moo Young has changed.

Both Moo Young and Jin Kang come to know about their past. After killing Se Ran, Moo Young asks Jin Gook to give him three days before turning himself in. Meanwhile, Jin Kang figures out where Moo Young is, and goes to find him and talk to him.