The story is set in contemporary South Korea. About 30 years ago, unidentified creatures appeared out of nowhere and began attacking people. They have caused massive destruction wherever they go. The monsters are called "Trouble," and their emergence has plunged the world into chaos. Along with the first appearance of the "Troubles," a number of humans were born with or acquired supernatural abilities. These mutants, called "Trace," are the only ones who can fight off the "Trouble." The "Trace" are also considered freaks and are generally shunned by the community because some of them misused their powers for their own interests. The plot revolves around two main characters. Sah Gang-kwon is a high school student born as a "Trace" who attempts to hide his ability. The other is Kim Yun-Seong, who acquired his "Trace" abilities during his early 30s. Soon after acquiring them, his wife and daughter were taken away from him for experimental purposes.