A modern criminal investigation expert unexpectedly transmigrates into ancient times, becoming a low-ranking retainer in a wealthy household. Just after waking up, he stumbles upon a bizarre murder and finds himself surrounded by suspicion. Relying on modern forensic knowledge, he gathers clues and solves mysterious cases. As turmoil spreads throughout the capital and various factions struggle against one another, crises arise one after another. Navigating between all kinds of people, he gradually uncovers layers of conspiracy while protecting those around him. Rising step by step, this commoner shakes up the imperial court and carves out his own path to success in a turbulent and unpredictable era.