Shen Du, a genius puppeteer born without the ability to feel pain, uses the forbidden Bone Pact to forcibly bind Xie Jinglan, the sole survivor of a massacre. They share each other's life and death, and the pact will last until one of them dies. From the moment it takes hold, Shen Du imprisons Xie Jinglan in a secret chamber of white bones and binds his limbs with puppet strings. Through the pain they feel together, Shen Du experiences the vividness of emotion for the first time. Xie Jinglan is resilient and unyielding, every desperate struggle turning into bone-deep hatred. Yet because of the Bone Pact, he cannot even choose his own fate alone.
Though they are enemies, they share a destiny, forming a twisted symbiosis through the tug-of-war between hatred and pain. When the truth finally comes to light and Shen Du is revealed not to be the real culprit, Xie Jinglan breaks down, while Shen Du comes to understand for the first time what it means to have a broken heart. Faced with the fated Formation of Ten Thousand Bones, the two go from opposing one another to standing side by side. In their final moments, they burn bone to seal their pact. Shen Du finally learns what it means to feel heartache, but the end awaits him too. At last, two skeletons who remained together until death embrace amid the ruins, their pact markings intertwined as they compose a tragic, beautiful swan song.
