During the Mad Hatter Masquerade, a fundraiser hosted by the Friends of the Opera on the grounds of the old Pendleton Grist Mill, Harlan Sadler, husband of Cricket Sadler, the chairwoman, is killed. He's been hit in the head with a croquet mallet, and his body hung on the chains and paddles of the grist mill. Nobody can figure out why since Harlan was much beloved by everyone. It's only after Cricket and Delaine beg Theodosia to investigate that she realizes the killer might have mistaken Harlan for his crazy son, Duke. After all, Duke is a slum landlord and recently injured a woman in a boating accident.