Conan and Kogoro are passing by an apartment building when they see a police car parked there. In the apartment, a woman who lived alone was found dead. Three fingerprints were found at the scene. The first was a man she was dating. The second belonged to the owner of the store where she worked. The other was not registered. Since there were no signs of prying at the front door or windows, the police began investigating the crime as being committed by a known acquaintance.