In 1900s Tianjin, a shipping magnate is found mysteriously drowned and chained underwater, and police dive captain Guo Deyou becomes the prime suspect. As the victim’s son, Ding Mao, investigates, more strange drownings occur, forcing him to team up with Guo, a spirit medium, and a journalist. Their search uncovers a dark secret tied to a deadly cult from decades ago, now resurfacing to wreak havoc. Together, they must uncover the truth and stop the rising threat.