A story where ten people get the chance to go back in time by one year, but unexpectedly mysterious situations start to arise when their fates are changed and twisted in the process.

After barely surviving a violent attack by an elusive serial killer, crime boss Jang Dong-su finds himself forming an unlikely partnership with local detective Jung Tae-seok to catch the sadistic killer simply known as "K".

An action drama about people who struggle to change their fate, one of whom is an elite detective with great analyzing skills.