The Dark River is a secret assassin organization jointly formed by the powerful Su, Xie, and Mu families, all ruled under the authority of the mysterious Grand Elders. When the Elders suddenly fall gravely ill from an unknown poison, internal chaos erupts as each family moves to seize control.
Su Mu Yu, the loyal leader of the Spider Shadow guard, must protect the weakened Elders from betrayal and assassination. To save them, he seeks the help of Bai He Huai, a renowned healer from Medicine King Valley. As rival factions close in and dark secrets surface, Su Mu Yu and Bai He Huai are drawn into a deadly struggle for truth, loyalty, and survival within the shadows of The Dark River.