He Yilin appears to be an ordinary programmer in a technology company, but is actually a top undercover agent deployed by the police among the evil forces. He is cold and taciturn, low-key in his actions, but has a chilling and decisive approach. This time, the task he received was to infiltrate the underground organization of "Humanity Experimenter" Shen Moyuan - a crazy criminal group that enjoys manipulating people's hearts and testing the bottom line of human nature. Shen Moyuan is keen on designing various extreme situations and observing the collapse of human nature between desire and fear. He Yilin pretended to be a recruited technical genius and approached the core step by step. However, what he didn't expect was that Shen Moyuan's adopted daughter Wen Qing would become the biggest variable in his plan. Wen Qing is innocent and innocent, but grew up in a dark environment. She developed an unsuspecting dependence and admiration for He Yilin. He Yilin must complete the undercover mission while protecting this girl who should not be stained in the daily life of sweetness and danger. When Shen Moyuan sets up the ultimate human nature test, targeting He Yilin and Wen Qing, he has no choice but to tear off the disguise.
