Detective Ji Bai and new criminal profiler Xu Xu may appear to be an odd teacher-student duo at first appearance, but they are the best collaborators in the police force, solving one crime after another. Ji Bai slowly falls in love with Xu Xu, despite the fact that she is a girl who loves as slowly as a snail. The latent "Angel's Killer" reappears just as Xu Xu is about to reciprocate Ji Bai's sentiments.