Conan, Kogoro, and Ran visit the home of client Nemoto Eriko. Three months ago, Eriko lost her husband, Nemoto Yutaka, in a traffic accident. While going through his things, she found 20 million yen in the back of the closet. Believing it could be dirty money, Eriko hired Kogoro to determine where the money came from. Kogoro considers the possibilities of savings or lottery winnings but eventually begins investigating armed robberies that took place recently. They narrow down the list of possible cases and visit the victims.