Ten years ago, Jiang Xun's parents entered a valley and never came out.
Ten years later, he stood at the entrance with half a bronze fragment. The people in town said the valley had an echo: call someone's name, and they would answer, even if they were dead.
Jiang Xun has eyes that can see the gaps between the present world and the "Old Track." The Old Track is an alternate dimension embedded in the same space. It leaks into the world, replicating voices, faces, and memories, and rewriting the physical laws of any place it touches: shadows move on their own, footprints come from tomorrow, and a kettle is filled with water from the valley floor during the night. Those who can see the gaps can take rules apart to survive, but the price is that every time they look, they forget a piece of themselves.
He meets two people. Wen Shuran studies toxicology and trusts only instruments and the written word. There is a scar on the back of her left hand that the Old Track cannot replicate. Kui Hu is the only person ever to crawl out of the Old Track alive. He fears anything that repeats and looks at Jiang Xun as if he were a time bomb.
Then there's Xuan Jizi. He doesn't kill people; he only uncovers the deepest regret in their hearts: "Your mother asked me to give you a message." Refusing comes at a price: another person dies, and another memory is stolen. He spent a thousand years trying to carve a passage into the Old Track, hoping to escape this world trapped in a cycle of suffering, never realizing that the Old Track itself is another kind of cycle.
The three of them distrust one another and check each other's perceptions, each pulling the others back just as the world is about to swallow them whole. "Do you remember the scar on my left hand?" "I do." "If the scar's still there, you haven't gone mad."
Five fissures, five sets of rules: Echo Valley, Lake of Layered Shadows, Chronology Post Station, Memory-Eating Forest, and the Endless Platform. There is no single monster. The horror lies in a world that makes no sense.