The third prince, Zhao Heng, grew up on the fringes of the cold palace. His biological mother died young and he had no relatives to support him. He was like a transparent person in the palace where the imperial power was strife. Only Taifu Shen Yanqiu occasionally gave advice. A strange disease breaks out in the palace. Those infected with the disease are covered with spiral red spots all over their bodies. They die screaming "Eye of the Deep Sea" every night. The imperial hospital is helpless, but the emperor orders the news to be blocked. When Zhao Heng is sweeping the grave of his biological mother, he accidentally discovers a spiral symbol consistent with the red spots of patients with the strange disease carved on the corner of the cold palace. He vaguely feels that something is fishy. However, he was regarded as a thorn in the side by the prince's gang members, who falsely accused him of hiding witchcraft and poison. Before he woke up from the nightmare, a greater crisis followed: the sick eunuch pointed out that Zhao Heng had been to the epidemic area before his death. The emperor was furious and grounded him. At this time, Shen Yanqiu died suddenly. He realized that this strange disease, the undercurrent of the palace, and even the survival of the entire dynasty were inseparable from the unknown existence in the deep sea, and he must uncover this shocking scam that spanned hundreds of years before he was swallowed up.
