In an abandoned warehouse, the head nurse Chen Lan died mysteriously. A neat "gantry knot" on her neck pointed the murderer to a group familiar with old-fashioned factory operations. This kind of knot, which is only popular in old factories, is like a cold password, kicking off a city-wide investigation - the task force decided to "one-size-fits-all" investigate male workers in all relevant factories and family homes. Tens of thousands of files were piled up, but clues were lost in the sea.
With only vague profiles (left-handed, knowledgeable about surgery, and withdrawn), the protagonist team struggled to sift through massive amounts of information. They went through employee files and interviewed retired workers. Every time they got closer to the truth, they were led astray by new disturbing clues. No one thought that the real murderer had already infiltrated the investigation team. Perhaps he was a factory technician who helped organize the files, or he was a volunteer at the family home who cooperated with the visit. He used his identity to skillfully tamper with information, guide the investigation, and perfectly hide his traces among tens of thousands of suspects. He even watched the protagonist team anxiously explore in the fog he had created.
When the key feature of "left-handedness" surfaced, the scope of the investigation continued to narrow, and the identity of the murderer gradually came closer - the person around him who was always "enthusiastic" in providing clues and seemed to be without suspicion actually hid the darkest secret. A cat-and-mouse game surrounding the "Gantry Knot" reaches a thrilling ending amidst the roar of the factory and the turning of files.
