Chen Guanlou, a modern-day overworked office worker, travels to the Great Xia dynasty and awakens an immortal Dao fruit, granting him eternal life despite being born without martial meridians. Seeking a stable livelihood, he takes over his father's position as a prison guard in the Imperial Heavenly Prison. Using his job to approach condemned prisoners, he secretly trains in forbidden martial arts, exploiting his immortal body to become powerful at an astonishing pace. As prison breaks, secret struggles within noble households, covert investigations by the Embroidered Uniform Guard, and political factional conflicts erupt one after another, he maintains a smooth-talking, money-minded, low-profile facade while secretly eliminating threats by turning enemies against one another. When his niece is kidnapped, he finally unleashes his full power, dismantles the human trafficking network, and rescues his family. Ultimately, he returns to the Heavenly Prison, conceals his true strength, and embarks on a path to becoming invincible in secret.