The police are unable to find the source of the poison from the drinks. As they are able to rule the death as a suicide, the black knight declares it was a murder and reveals his identity to be Shinichi. Shinichi reveals that the poison was placed in the ice cubes and that Mazuda had a habit of eating ice. He reveals the murderer to be Mazuda's friend, Mai Kougami. Shinichi explains that Mai kept the ice cubes in a little purse which was kept cool through dry ice. Mai says that she bought the same drink as Mazuda and that there was only a fifty percent chance that he would take the drink with the poisoned ice cubes. Shinichi explains she put ice cubes in both drinks and that after emptying her drink, she placed the poisoned ice cubes in her hood evidenced when a 10 yen coin undergoes a chemical reaction with contact to her hood. Mai confesses and explains that Mazuda murdered his patient in order to have his medical thesis published. Shinichi collapses after solving the case and wakes up and realizes he still retains he is still Shinichi and has not regressed back to Conan.