"Special Affairs Team TEN" is a criminal investigation unit that tackles the most violent, hardcore crimes in South Korea.

Following the motto of "No more unsolved cases," the detectives chase those who attempt to commit the perfect crime, facing some of the most twisted and perverted criminals that they have ever encountered in their careers.

Yeo Ji-hoon (Joo Sang-wook) was a former ace detective with keen deductive powers and a strong logical mind, who now works as a police academy instructor.

The team includes: Nam Ye-ri (Jo An), a profiling specialist; Baek Do-shik (Kim Sang-ho), a veteran cop who possesses a keen sense of intuition, which he honed from 24 years on the job, and who good-naturedly chides the team to always treat people like human beings; and Park Min-ho (Choi Woo-shik), a "pretty boy" rookie who impressed Ji-hoon in class, and is the man on the ground who does all the running and grunt work.

The other members of the team, Baek Do-shik, Nam Ye-ri and Park Min-ho are initially confused by the situation, but they soon find a message which explains Ji-hoon's intentions.