Kogoro appears in a commercial to promote white chocolate for White Day and is invited to a chocolate company's party. Kogoro, Ran, and Conan attend and are introduced to the company presidents, Taruto Urai and his wife Hoshie Urai. During the party, Taruto dies from cyanide poisoning. Inspector Megure and his Officers are called to investigate the death. The investigation leads Hoshie to be the prime suspect. As she is taken away to be searched, Hoshie trips and falls on a table causing many lemon tea glasses to shatter. Meanwhile, evidence of a medicinal wafer containing poison is found in Urai's mouth suggesting suicide. Conan is ascertain Hoshie to be the culprit and investigates on how she delivered the poison to her husband.