Two murders occur at the event hall where Kogoro is scheduled to attend a speaking event. Kogoro accuses former hall manager Reizei of murdering actor Inokoshi Kenichiro, but he confesses to the murder of event hall owner Hishida Junko instead. The lecture is delayed an hour until Kogoro can determine the identity of the real culprit. However, everyone except for Reizei has an alibi for the time of the murder, leaving Megure and Kogoro without any suspects.