The continuous rain washed away the neon lights of the city and erased the last key fingerprint at the crime scene. Criminal investigation captain Lin Yan squatted in the damp alley, and his fingertips traced the water stains remaining on the glass fragments - the traces that should have identified the murderer disappeared without a trace, like secrets swallowed by the rain.
Within three months, the third "traceless murder" occurred on a rainy day. The victims seemed unrelated, but they all came into contact with a silver ring engraved with fleur-de-lis before their deaths. When Lin Yan followed the clues of the silver ring and found the clockmaker living in seclusion in the old city, the other person only left a sentence: "Fingerprints on rainy days will return to where they belong", and then disappeared mysteriously in the rainy night.
