Synopsis: Top student Xu Lang (Zhang Chao), specializing in Criminal Psychology, received his Ph.D. from the University of Maryland. After returning to China, he began working at the Public Security Bureau, but was seriously injured and even lost his younger brother during the investigation. Seven years later, as the youngest professor, Xu Lan teaches criminology at the National Police Academy. Xu Lang’s friend Tan Sen (Li Chen Hao) invites him to return to the field and help the newly established criminal psychology group “X”. The team is working on unsolved cases, as well as finding new clues in the case that changed Xu Lang’s life seven years ago.