With the appearance of the "Gate of Hell", the beautiful starry sky was covered up, and replaced by a false starry sky used to monitor the actions of the "Contractors". "Contractors" are people who gain superpowers after coming into contact with the substances in the "Gate of Hell". As the chosen people, they are cold and ruthless, which makes people full of fear and doubt. Various mysterious organizations use the superpowers of contractors to fight for their own interests. Hei, who was not originally a contractor, had to join the battle against his will for the sake of his sister Bai, and fell in love with the contractor Amber. But he gradually discovered that Amber betrayed the organization and himself; after the mysterious incident, his sister also disappeared. The angry Hei finally became a real contractor, known as the Black Death and the cursed contractor. In the execution of the organization's mission, Hei met Amber again, and Amber's words and deeds became more mysterious, as if there were many unspeakable secrets under the betrayal. In order to find his sister, Hei tracked Amber and gradually saw the bigger secrets behind the melee. Can Hei find his sister? What choice should he make for the fate of himself and the contractor?