The son of a world famous mystery writer, Jimmy Kudo, has achieved his own notoriety by assisting the local police as a student detective. He has always been able to solve the most difficult of criminal cases using his wits and power of reason. Kudo Shinichi is a seventeen year-old high school detective whom people call the \"Modern Sherlock Holmes.\" However, one night after a date with his childhood sweetheart, Ran, Shinichi witnessed an illegal trade and, caught off his guard, was knocked unconscious and fed a drug that was supposed to kill him... but he woke up and found himself shrunken to a seven year-old. In order to track down the men who did this to him, Shinichi hid his identity and lived with Ran, whose father happened to be a hopeless detective, and with that came a series of murders and mysteries that he must solve.