The Liar Hunter Mok Sol-hee uses her special power to make money. One day when she is running away to Seoul, she meets a mysterious boy on the bus. Although he is just a random person to her, she later finds out far in the future that he is the worldwide famous composer Kim Do-ha.

Sol-hee helps Do-ha escape from the town residents. But she later finds out that he is a new neighbor who moves into the apartment where Sol-hee lives. Meanwhile, Deuk-chan gets blackmailed by Moo-jin. By force, he sets up a meeting where Do-ha must face Moo-jin face to face. To uncover his secrets, Moo-jin hires Sol-hee to come to the meeting.

Sol-hee feels bad that Do-ha has not returned home after that incident. After a few days, Do-ha and Sol-hee run into each other in front of their apartment. Meanwhile, Syaon ends up in a hospital after she sprains her ankle on stage. Sol-hee's mother tries to get some pocket money from Sol-hee by giving false excuses without getting caught.

Sol-hee let Do-ha hide in her apartment to dodge the reporters. Then Sol-hee realizes that he has not told a single lie to her so far, and she is confused about whether her ability does not work on him or he is telling the truth. Therefore, Sol-hee tries to hang out with him more often to make him say a lie. Meanwhile, Kang-min receives a report at Sol-hee's apartment.

Sol-hee finally hears Do-ha's first lie, which is the most unexpected and terrifying to find out. Sol-hee decides to stay out of his life now that she figured out her ability works well on him, and he is also an ordinary person, but she can't stop thinking about him. Meanwhile, a man with a mask posts a video of him, saying he is Kim Do-ha.

With the help of Sol-hee, Do-ha stops covering his face with a mask outside. Their feelings for each other grow stronger as they go through challenges together. Just when everything seems perfect, Sol-hee runs into her mother while working for one of her clients, and someone comes to see Deuk-chan to ask about Do-ha.

Even though Sol-hee confessed her ability to Do-ha, he stays closer to her and treats her the same, unlike everybody else. Both Sol-hee and Do-ha finally have each other who they can trust and rely on. Meanwhile, Do-ha and Sol-hee visit Yeonseo Bakery and find something fishy about a customer.

Whenever Do-ha denies that he committed murder, Sol-hee can hear that it is a lie. It breaks her heart as she believed he is the only person who does not lie about anything, yet he told her the worst lie of all. Meanwhile, Deuk-chan wants Do-ha to move out of the apartment and stay away from Sol-hee now that she finds out about Seung-ju.

Do-ha tells Sol-hee everything about what happened back in his hometown with Eom-ji. Do-ha clears up the misunderstanding and returns to his apartment in Yeonseo-dong with Sol-hee. Meanwhile, Kang-min finds out about the Hakcheon Beach case, and Eom-ho gets to Syaon.

Kang-min saves Do-ha from Eom-ho. He warns Do-ha to keep Sol-hee safe and not to let her find out about the incident. Meanwhile, Deuk-chan tells Yeon-mi about Sol-hee. Yeon-mi visits Sol-hee's cafe and sees Do-ha and Sol-hee together.

Bones get discovered on a mountainside in Hakcheon, and the police get called to investigate. Kang-min thinks it could be the skeleton of Choi Eom-ji, the missing girl. As he waits for DNA analysis to finish, Kang-min asks Sol-hee about Seung-ju one last time. Meanwhile, J Entertainment ends it's relationship with Do-ha and Syaon.

The public discovers that Do-ha is the primary suspect in the case, and he becomes the public target. People are quick to point fingers and criticize him. Fed up with the situation, Do-ha decides he will no longer wait and take matters into his own hands. He decides to find the culprit himself to clear his name.

Do-ha successfully located Eom-ji's father, Yong-guk, whom Do-ha suspects to be the prime suspect. Yong-guk admits that he had hoped for Eom-ji's death to claim her insurance money but denies being involved in her murder. He reveals to Do-ha that Jae-chan used to constantly follow Eom-ji around.

Jo Jae-chan turns himself in to the police and confesses to the murder of Eom-ji. With the culprit now in custody, Do-ha and Sol-hee celebrate with their friends for Do-ha proving his innocence. While they can resume their usual life, Do-ha still has lingering unease in his mind. So Do-ha and Sol-hee decide to investigate further.

Sol-hee wakes up in the hospital without any issues from the accident. Luckily, Jae-chan also survives after undergoing surgery, and finally, he gets to tell Do-ha the truth about what happened that night with Eom-ji. Later, Sol-hee learns she's lost her ability and learns to cope with living without it.

Tae-seop stops Hyang-suk from marrying a man she doesn't love and proposes to her. But Hyang-suk turns him down, telling him harsh things she doesn't really mean. Right then, Sol-hee's ability to detect lies comes back again. Meanwhile, Do-ha gives Ethan a song as a gift and helps produce his first solo album.