Jeon Jihoon, a talented student studying profiling, gets a chance to do an internship under the experienced detective at the Busan police department. At the same time, a series of brutal murders are happening in the city, committed by a mysterious criminal known in the media as "Moon Butterfly". The ruthless killer leaves no trace, as if fluttering in the night, causing a wave of fear among the residents.

However, as the investigation progresses, Jihoon suddenly realizes that the shadow of the Moon Butterfly is much closer than he could have imagined.

"Shadow of a Moon Butterfly" is a gripping psychological thriller about revenge and the cruelty that can hide behind the most impeccable mask.