Amidst a series of murders that appear to be committed by the Phantom, the same mask worn by Leona Kozuki's attacker is found in Jo's room. The members take turns safeguarding the key to the theater. However, by the time Kindaichi, Saki, and Leona enter to bring food to the lone man, they find that he has been murdered. Kindaichi's frustration grows as he struggles to solve the mystery of the locked room murder. Meanwhile, Kenmochi notices that something is amiss at the tower where the Phantom ambushed him. Kindaichi swears on his grandfather's name to uncover the true identity of the Phantom, the killer responsible for three deaths.
