Only the River Flows

In 1995, police captain Ma Zhe investigates the murder of an elderly woman called Granny Four in a small riverside town in rural China. The main suspect is a mentally ill drifter she had adopted, known only as “the madman.” During the investigation, Ma Zhe discovers a cassette tape containing emotional recordings between two secret lovers, Qian Ling and Wang Hong. The tape leads the police into hidden relationships, poetry gatherings, and clues about a mysterious woman with long wavy hair seen near the crime scene. Before the mystery is solved, Wang Hong is murdered in the same way as Granny Four, making the case more complicated.

As pressure from police superiors grows, Ma Zhe investigates several suspects, including Xu Liang, a troubled hairdresser with a criminal past who strangely keeps asking the police to arrest him. Meanwhile, the madman is institutionalized, and the authorities want the case closed quickly. Ma Zhe, however, feels the evidence does not fully fit together. At the same time, his personal life deteriorates. His wife’s pregnancy may involve a genetic disorder in the baby, causing emotional conflict between them. Ma Zhe becomes increasingly obsessed, exhausted, and mentally unstable as he replays the cassette tapes and tries to understand the hidden connections between the murders.

The climax happens after the madman escapes from a psychiatric hospital and kills the young boy who first found Granny Four’s body. During a final manhunt near an abandoned temple, Ma Zhe shoots and kills the madman. But afterward, he tells his chief that he believes the madman intentionally arranged events so that Ma Zhe himself would become the one to kill him. Despite Ma Zhe’s doubts and confusion, the police officially declare the case solved, praise him as a hero, and award him a merit honor. The ending leaves the truth uncertain, with Ma Zhe psychologically damaged and unable to separate reality, coincidence, institutional pressure, and fate.

• Zhu Yilong as Ma Zhe
• Chloe Maayan as Bai Jie
• Hou Tianlai as the Chief of Police
• Tong Linkai as Xie

Just before principal photography, the COVID-19 pandemic in China was surging again, and the entire cast and crew was put on lockdown. The team had around 45 days of preparation and approximately 45 days of shooting, and had to pause for two days when Wei and Zhu tested positive.^[10]

Principal photography began in Nanfeng, Jiangxi, on 19 December 2022, and wrapped in early February 2023. "The film was shot mostly in chronological order as same as in the script".^[7]

Zhu Yilong gained weight during the preparation to give the character a heavyset appearance from overwork. He lost 55 pounds during the 45 days of shooting as the shooting went on.

Almost the entire film was shot on 16 mm film.^[11]

Speaking to Amy Hawkins of The Guardian, Wei said of Yu's book the following: "A detective novel is supposed to be based on rationality and logic, [but in Mistakes by the River there is a] different understanding of rationality … we're thinking about the limits of rationality. I found that very appealing."^[12]