Cui Xun, played by Zhang Yi, works with a forensic pathologist and a veteran detective to solve cases that have baffled the police, using bite marks, fingerprints, fibres, firearms evidence and other overlooked details. Partly set in Harbin, the story spans decades, showing how investigation techniques evolved from painstaking manual work to modern science. The real Cui Daozhi spent more than fifty years in law enforcement and examined more than 7,000 pieces of evidence, becoming one of the Ministry of Public Security's first specially invited criminal investigation experts. Directed and co-written by Chen Sicheng, one of China's most commercially successful film-makers, known for the Detective Chinatown series, Traces of Justice topped the Chinese box office on its opening day during the National Day holiday. Zhang Yi, a respected character actor, leads a cast that includes Ma Li and Chen Minghao.