The series follows the lives of a kind veterinarian and a grumpy detective. Bong Ye-boon (Han Ji-min) is a veterinarian who has psychic abilities. She can see the past of any person or animal when she touches their rear end. On the go, she meets Detective Moon Jang-yeol (Lee Min-ki) and gets intertwined in cases. Jang-yeol is demoted to the rural village Mujin due to being a terrific hothead back in Seoul. To return back to the city, he seeks Ye-boon and starts uncovering various cases. However, their fate changes when Kim Sun-woo (Suho) arrives at Mujin and works at a grocery store. Though he seems kind and polite, he has deadly mysteries behind him.
Jang-yeol and Ye-boon immediately go to Gwang-sik’s house to check on him and learn from Ae-ran that he has gone out for something. Jang-yeol drops Ye-boon at her home and advises her to stay to call Ok-hee and stick along. Jang-yeol tries to find Gwang-sik and comes across the serial killer. When he chases him he understands that the serial killer is not Gwang-sik. When Jang-yeol tries to attack him and find the killer’s identity he somehow escapes.
Back at Ye-boon’s hospital/home, a bloody Gwang-sik comes and tries to give a hint about the killer to her. He says “black” before passing away. Jang-yeol rushes to Sun-woo’s home and starts to search his place. Since he spots blood on Sun-woo’s hands, he tries to make him accept he is the killer. Sun-woo stops Jang-yeol and asks for the search warrant and evidence. The latter challenges he’ll soon find him guilty.
That very night, Ye-boon tells Jang-yeol about Gwang-sik’s last words to her. Jang-yeol reveals that the killer must have blackouts and that’s what Gwang-sik would have tried to tell. Jang-yeol explains to her how he tried to check how one can kill with their eyes closed. He then requests Ye-boon to stay away from Sun-woo no matter what.
However, Ye-boon decides to meet Sun-woo to check on him once again. The two meet at the neighbourhood park and Sun-woo asks her to check him again because he doesn’t want her to suspect him. She tells him that she trusts him which eases his heart. Ye-boon then shares details regarding the killer and them being a psychic. Sun-woo thinks about something when she conveys the details.
Jang-yeol, Jang-mook, and Dok-hee test out the blackout tricks but fail to find the exact method. Jang-yeol requests Jang-mook to check on Gwang-sik’s corpse to see the stab marks and they learn that the killer’s skills have gotten better. A video of Jang-mook sneaking into the autopsy room causes them to leave Mujin to attend another case. Jang-yeol becomes mad at the thought of letting the Seoul police handle the serial killer case.
Meanwhile, Sun-woo and Ye-boon get close as she believes he isn’t the killer and he feels comfortable around her since she is the only one who trusts him. Seeing them two together, Jang-yeol asks Ye-boon to date him if she wants to date someone. This irritates Ye-boon. Jang-mook asks the Shaman to check Sun-woo thoroughly and find the weapon. However, Sun-woo catches the Shaman’s weird actions.
Before leaving Mujin, Jang-yeol ensures Ye-boon stays locked in the police station cell for protection. But she somehow escapes and leaves for her home. Ok-hee informs about her escape to Jang-yeol and he returns to Mujin. Ye-boon gets a call from Sun-woo and she leaves to see him.
At the workshop, Sun-woo looks at the bloody knife and waits for Ye-boon. When he sees her entering with the Shaman he immediately closes the toolbox, arousing Ye-boon’s suspicion. When Sun-woo steps out with the Shaman, she opens the toolbox and sees the knife. She immediately escapes. Sun-woo returns to the workshop and runs behind Ye-boon with the knife.
Suddenly in front of her, she sees another person wearing the rain poncho. It is understood that Sun-woo isn’t the killer but he ran behind her to save her. He asks her to escape and he fights with the serial killer. When Ye-boon returns to the spot to check on Sun-woo, she finds him lying down in a pool of blood.