In 1937, in Los Angeles Chinatown, police officer Jack (Jack Nicholson) quit his job and became a private detective because he was dissatisfied with the darkness here. One day, a woman who called herself Mrs. Morales asked Jack to investigate her husband's affair, and Jack gladly accepted. Jack found out that Morales was the chief engineer of the local water conservancy and was arguing with local farmers over the construction of a dam. Then someone gave Jack some photos proving that Morales was having an affair, but the next morning the real Mrs. Morales came to ask Jack to stop investigating Morales. Things became more and more confusing, and Jack was determined to track it down...