In a modern metropolis, a professional private suspense reasoning team is hired to assist the police, media or private individuals in solving various "difficult cases". They cross-border integration of psychological analysis, criminal investigation, forensic science, technical investigation and legal consultation. There are unknown secrets hidden behind each case. Team members grow and break during the process of reasoning and investigation, gradually uncovering the shadows in themselves and others. As many seemingly unrelated mysteries were gradually revealed, the team discovered that there was actually a larger black hand behind all the cases. In the end, they will face the ultimate mystery and start a desperate battle with the "sin" hidden in the deepest part of the city.
