Shinichi loses a game against Ran and Sonoko during lunch so now he must play a penalty game: he must accept every request for a favor for the rest of the day. Before Ran can ask for Shinichi to take her out to a restaurant, Kogoro calls Shinichi and asks for him to assist with the wedding party of Kensuke Motoki and Kanon Shimabara. Later on, one of the guests, Nana Matsumoto, drops dead from what seems to be poison. Kensuke asks for Shinichi to prove his innocence, but is this one favor Shinichi can't complete?