Sako Manabu, a man with bloody clothes, arrives at the Mori Detective Agency. After a series of unfortunate events, yesterday Sako went out to drown his sorrows, but he can't remember what happened. When he woke up, his glasses were broken and his clothes were covered with blood. He only had a bump on his head, so he realized the blood belonged to someone else. Concerned that he might have done something terrible, he sought help. Though they initially believe there are no clues, Conan finds hints on Sako's body.