Fourth Witness

Detective Gu Yuan's mother disappeared ten years ago, leaving behind a table of cold meals. Ten years later, the old building was about to be demolished. Gu Yuan opened the door for the last time - there was hot braised pork on the dining table, and a note from his mother pressed beside the bowl: "The meal is ready, waiting for your return." Same day, same date. He began to trace. A man in a gray jacket has appeared at the scene of every disappearance for forty years. The first missing person, Li Xiuying, had met him, her mother had met him, and her uncle Gu Jianjun, who had disappeared for many years, was also related to him. And all clues point to the locked door. What's behind the door? Some said he had been locked up for thirty-eight years, some said he saw three men in gray jackets standing downstairs, and some said they were his future selves. The mother's voice came from the phone: "Xiaoyuan, is the food delicious?" But she disappeared ten years ago. Gu Yuan pushed open the door. At the end of the corridor, countless doors extend into the invisible distance. Behind each door is a "self" - young, middle-aged, and young. They are waiting for him. Last question: Whose is that gray jacket? Some answers are not in the book.