Genius student Xu Lang who specializes in Criminal Psychology obtained a PhD at the University of Maryland. After returning to China, he joins the public security bureau but is severely injured and even loses his younger brother while solving a case. Seven years later, Xu Lang is the youngest professor of Criminology at the National Police University. Then, his friend Tang Sen invites him to return to the field and help out their newly established "Criminal Psychology Team X". Together, the team of four uncovers unsolved cases and also finds new clues in Xu Lang's life-changing case from seven years ago.