Shinichi Kudo is a high school detective who sometimes works with the police to solve cases.
During an investigation, he is ambushed and incapacitated by a member of a crime syndicate known as the Black Organization. 
In an attempt to murder the young detective Shinichi, they force-fed him a dangerous experimental drug APTX4869. 
However, instead of killing him, it shrinks his body to the size of an elementary school child.
Adopting the pseudonym Conan Edogawa and keeping his true identity a secret, Kudo lives with his childhood friend Mori Ran and her father Kogoro Mori, who is a private detective. 
Throughout the series, he tags along on Detective Kogoro's cases while trying to expose the substance of the black organization.