In the small town of Meiyu in the south of the Yangtze River, on a rainy night twenty years ago, six teenagers witnessed a murder under the seventh bridge, but chose to remain silent. Twenty years later, an unknown body of a man appeared on the seventh bridge, holding a group photo of that year tightly in his hand. The county criminal police captain Shen Mo - one of the six witnesses that year - was forced to return to his hometown to investigate the case. As the investigation deepens, the crimes committed twenty years ago gradually come to light: it was not a murder, but a righteous lynching that was collectively covered up. When the truth was revealed, Shen Shen discovered that the deceased was the only son of the "deceased". He came back not for revenge, but to let six witnesses personally judge the seventh real sinner - the one who instigated everything back then and now has become the highly respected mayor of Shen Shen.
